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commit 89affbf5d9ebb15c6460596822e8857ea2f9e735 upstream.
In codepaths that use the begin/retry interface for reading
mems_allowed_seq with irqs disabled, there exists a race condition that
stalls the patch process after only modifying a subset of the
static_branch call sites.
This problem manifested itself as a deadlock in the slub allocator,
inside get_any_partial. The loop reads mems_allowed_seq value (via
read_mems_allowed_begin), performs the defrag operation, and then
verifies the consistency of mem_allowed via the read_mems_allowed_retry
and the cookie returned by xxx_begin.
The issue here is that both begin and retry first check if cpusets are
enabled via cpusets_enabled() static branch. This branch can be
rewritted dynamically (via cpuset_inc) if a new cpuset is created. The
x86 jump label code fully synchronizes across all CPUs for every entry
it rewrites. If it rewrites only one of the callsites (specifically the
one in read_mems_allowed_retry) and then waits for the
smp_call_function(do_sync_core) to complete while a CPU is inside the
begin/retry section with IRQs off and the mems_allowed value is changed,
we can hang.
This is because begin() will always return 0 (since it wasn't patched
yet) while retry() will test the 0 against the actual value of the seq
counter.
The fix is to use two different static keys: one for begin
(pre_enable_key) and one for retry (enable_key). In cpuset_inc(), we
first bump the pre_enable key to ensure that cpuset_mems_allowed_begin()
always return a valid seqcount if are enabling cpusets. Similarly, when
disabling cpusets via cpuset_dec(), we first ensure that callers of
cpuset_mems_allowed_retry() will start ignoring the seqcount value
before we let cpuset_mems_allowed_begin() return 0.
The relevant stack traces of the two stuck threads:
CPU: 1 PID: 1415 Comm: mkdir Tainted: G L 4.9.36-00104-g540c51286237 #4
Hardware name: Default string Default string/Hardware, BIOS 4.29.1-20170526215256 05/26/2017
task: ffff8817f9c28000 task.stack: ffffc9000ffa4000
RIP: smp_call_function_many+0x1f9/0x260
Call Trace:
smp_call_function+0x3b/0x70
on_each_cpu+0x2f/0x90
text_poke_bp+0x87/0xd0
arch_jump_label_transform+0x93/0x100
__jump_label_update+0x77/0x90
jump_label_update+0xaa/0xc0
static_key_slow_inc+0x9e/0xb0
cpuset_css_online+0x70/0x2e0
online_css+0x2c/0xa0
cgroup_apply_control_enable+0x27f/0x3d0
cgroup_mkdir+0x2b7/0x420
kernfs_iop_mkdir+0x5a/0x80
vfs_mkdir+0xf6/0x1a0
SyS_mkdir+0xb7/0xe0
entry_SYSCALL_64_fastpath+0x18/0xad
...
CPU: 2 PID: 1 Comm: init Tainted: G L 4.9.36-00104-g540c51286237 #4
Hardware name: Default string Default string/Hardware, BIOS 4.29.1-20170526215256 05/26/2017
task: ffff8818087c0000 task.stack: ffffc90000030000
RIP: int3+0x39/0x70
Call Trace:
<#DB> ? ___slab_alloc+0x28b/0x5a0
<EOE> ? copy_process.part.40+0xf7/0x1de0
__slab_alloc.isra.80+0x54/0x90
copy_process.part.40+0xf7/0x1de0
copy_process.part.40+0xf7/0x1de0
kmem_cache_alloc_node+0x8a/0x280
copy_process.part.40+0xf7/0x1de0
_do_fork+0xe7/0x6c0
_raw_spin_unlock_irq+0x2d/0x60
trace_hardirqs_on_caller+0x136/0x1d0
entry_SYSCALL_64_fastpath+0x5/0xad
do_syscall_64+0x27/0x350
SyS_clone+0x19/0x20
do_syscall_64+0x60/0x350
entry_SYSCALL64_slow_path+0x25/0x25
Link: http://lkml.kernel.org/r/20170731040113.14197-1-dmitriyz@waymo.com
Fixes: 46e700abc44c ("mm, page_alloc: remove unnecessary taking of a seqlock when cpusets are disabled")
Signed-off-by: Dima Zavin <dmitriyz@waymo.com>
Reported-by: Cliff Spradlin <cspradlin@waymo.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christopher Lameter <cl@linux.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 5c0338c68706be53b3dc472e4308961c36e4ece1 upstream.
The combination of WQ_UNBOUND and max_active == 1 used to imply
ordered execution. After NUMA affinity 4c16bd327c74 ("workqueue:
implement NUMA affinity for unbound workqueues"), this is no longer
true due to per-node worker pools.
While the right way to create an ordered workqueue is
alloc_ordered_workqueue(), the documentation has been misleading for a
long time and people do use WQ_UNBOUND and max_active == 1 for ordered
workqueues which can lead to subtle bugs which are very difficult to
trigger.
It's unlikely that we'd see noticeable performance impact by enforcing
ordering on WQ_UNBOUND / max_active == 1 workqueues. Let's
automatically set __WQ_ORDERED for those workqueues.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Christoph Hellwig <hch@infradead.org>
Reported-by: Alexei Potashnik <alexei@purestorage.com>
Fixes: 4c16bd327c74 ("workqueue: implement NUMA affinity for unbound workqueues")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 3c74541777302eec43a0d1327c4d58b8659a776b upstream.
While refactoring, f7b2814bb9b6 ("cgroup: factor out
cgroup_{apply|finalize}_control() from
cgroup_subtree_control_write()") broke error return value from the
function. The return value from the last operation is always
overridden to zero. Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 7af608e4f9530372aec6e940552bf76595f2e265 upstream.
On subsystem registration, css_populate_dir() is not called on the new
root css, so the interface files for the subsystem on cgrp_dfl_root
aren't created on registration. This is a residue from the days when
cgrp_dfl_root was used only as the parking spot for unused subsystems,
which no longer is true as it's used as the root for cgroup2.
This is often fine as later operations tend to create them as a part
of mount (cgroup1) or subtree_control operations (cgroup2); however,
it's not difficult to mount cgroup2 with the controller interface
files missing as Waiman found out.
Fix it by invoking css_populate_dir() on the root css on subsys
registration.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 96b777452d8881480fd5be50112f791c17db4b6b upstream.
Commit:
2f5177f0fd7e ("sched/cgroup: Fix/cleanup cgroup teardown/init")
.. moved sched_online_group() from css_online() to css_alloc().
It exposes half-baked task group into global lists before initializing
generic cgroup stuff.
LTP testcase (third in cgroup_regression_test) written for testing
similar race in kernels 2.6.26-2.6.28 easily triggers this oops:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: kernfs_path_from_node_locked+0x260/0x320
CPU: 1 PID: 30346 Comm: cat Not tainted 4.10.0-rc5-test #4
Call Trace:
? kernfs_path_from_node+0x4f/0x60
kernfs_path_from_node+0x3e/0x60
print_rt_rq+0x44/0x2b0
print_rt_stats+0x7a/0xd0
print_cpu+0x2fc/0xe80
? __might_sleep+0x4a/0x80
sched_debug_show+0x17/0x30
seq_read+0xf2/0x3b0
proc_reg_read+0x42/0x70
__vfs_read+0x28/0x130
? security_file_permission+0x9b/0xc0
? rw_verify_area+0x4e/0xb0
vfs_read+0xa5/0x170
SyS_read+0x46/0xa0
entry_SYSCALL_64_fastpath+0x1e/0xad
Here the task group is already linked into the global RCU-protected 'task_groups'
list, but the css->cgroup pointer is still NULL.
This patch reverts this chunk and moves online back to css_online().
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 2f5177f0fd7e ("sched/cgroup: Fix/cleanup cgroup teardown/init")
Link: http://lkml.kernel.org/r/148655324740.424917.5302984537258726349.stgit@buzz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit dea1d0f5f1284e3defee4b8484d9fc230686cd42 upstream.
The move of the unpark functions to the control thread moved the BUG_ON()
there as well. While it made some sense in the idle thread of the upcoming
CPU, it's bogus to crash the control thread on the already online CPU,
especially as the function has a return value and the callsite is prepared
to handle an error return.
Replace it with a WARN_ON_ONCE() and return a proper error code.
Fixes: 9cd4f1a4e7a8 ("smp/hotplug: Move unparking of percpu threads to the control CPU")
Rightfully-ranted-at-by: Linux Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 9cd4f1a4e7a858849e889a081a99adff83e08e4c upstream.
Vikram reported the following backtrace:
BUG: scheduling while atomic: swapper/7/0/0x00000002
CPU: 7 PID: 0 Comm: swapper/7 Not tainted 4.9.32-perf+ #680
schedule
schedule_hrtimeout_range_clock
schedule_hrtimeout
wait_task_inactive
__kthread_bind_mask
__kthread_bind
__kthread_unpark
kthread_unpark
cpuhp_online_idle
cpu_startup_entry
secondary_start_kernel
He analyzed correctly that a parked cpu hotplug thread of an offlined CPU
was still on the runqueue when the CPU came back online and tried to unpark
it. This causes the thread which invoked kthread_unpark() to call
wait_task_inactive() and subsequently schedule() with preemption disabled.
His proposed workaround was to "make sure" that a parked thread has
scheduled out when the CPU goes offline, so the situation cannot happen.
But that's still wrong because the root cause is not the fact that the
percpu thread is still on the runqueue and neither that preemption is
disabled, which could be simply solved by enabling preemption before
calling kthread_unpark().
The real issue is that the calling thread is the idle task of the upcoming
CPU, which is not supposed to call anything which might sleep. The moron,
who wrote that code, missed completely that kthread_unpark() might end up
in schedule().
The solution is simpler than expected. The thread which controls the
hotplug operation is waiting for the CPU to call complete() on the hotplug
state completion. So the idle task of the upcoming CPU can set its state to
CPUHP_AP_ONLINE_IDLE and invoke complete(). This in turn wakes the control
task on a different CPU, which then can safely do the unpark and kick the
now unparked hotplug thread of the upcoming CPU to complete the bringup to
the final target state.
Control CPU AP
bringup_cpu();
__cpu_up() ------------>
bringup_ap();
bringup_wait_for_ap()
wait_for_completion();
cpuhp_online_idle();
<------------ complete();
unpark(AP->stopper);
unpark(AP->hotplugthread);
while(1)
do_idle();
kick(AP->hotplugthread);
wait_for_completion(); hotplug_thread()
run_online_callbacks();
complete();
Fixes: 8df3e07e7f21 ("cpu/hotplug: Let upcoming cpu bring itself fully up")
Reported-by: Vikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Sewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1707042218020.2131@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Commit ff86bf0c65f1 ("alarmtimer: Rate limit periodic intervals") sets a
minimum bound on the alarm timer interval. This minimum bound shouldn't
be applied if the interval is 0. Otherwise, one-shot timers will be
converted into periodic ones.
Fixes: ff86bf0c65f1 ("alarmtimer: Rate limit periodic intervals")
Reported-by: Ben Fennema <fennema@google.com>
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Cc: stable@vger.kernel.org
Cc: John Stultz <john.stultz@linaro.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit db9108e054700c96322b0f0028546aa4e643cf0b upstream.
Hit the kmemleak when executing instance_rmdir, it forgot releasing
mem of tracing_cpumask. With this fix, the warn does not appear any
more.
unreferenced object 0xffff93a8dfaa7c18 (size 8):
comm "mkdir", pid 1436, jiffies 4294763622 (age 9134.308s)
hex dump (first 8 bytes):
ff ff ff ff ff ff ff ff ........
backtrace:
[<ffffffff88b6567a>] kmemleak_alloc+0x4a/0xa0
[<ffffffff8861ea41>] __kmalloc_node+0xf1/0x280
[<ffffffff88b505d3>] alloc_cpumask_var_node+0x23/0x30
[<ffffffff88b5060e>] alloc_cpumask_var+0xe/0x10
[<ffffffff88571ab0>] instance_mkdir+0x90/0x240
[<ffffffff886e5100>] tracefs_syscall_mkdir+0x40/0x70
[<ffffffff886565c9>] vfs_mkdir+0x109/0x1b0
[<ffffffff8865b1d0>] SyS_mkdir+0xd0/0x100
[<ffffffff88403857>] do_syscall_64+0x67/0x150
[<ffffffff88b710e7>] return_from_SYSCALL_64+0x0/0x6a
[<ffffffffffffffff>] 0xffffffffffffffff
Link: http://lkml.kernel.org/r/1500546969-12594-1-git-send-email-chuhu@redhat.com
Fixes: ccfe9e42e451 ("tracing: Make tracing_cpumask available for all instances")
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 6a8a75f3235724c5941a33e287b2f98966ad14c5 upstream.
This reverts commit cc1582c231ea041fbc68861dfaf957eaf902b829.
This commit introduced a regression that broke rr-project, which uses sampling
events to receive a signal on overflow (but does not care about the contents
of the sample). These signals are critical to the correct operation of rr.
There's been some back and forth about how to fix it - but to not keep
applications in limbo queue up a revert.
Reported-by: Kyle Huey <me@kylehuey.com>
Acked-by: Kyle Huey <me@kylehuey.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20170628105600.GC5981@leverpostej
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 2e028c4fe12907f226b8221815f16c2486ad3aa7 upstream.
My static checker complains that if "func" is NULL then "clear_filter"
is uninitialized. This seems like it could be true, although it's
possible something subtle is happening that I haven't seen.
kernel/trace/ftrace.c:3844 match_records()
error: uninitialized symbol 'clear_filter'.
Link: http://lkml.kernel.org/r/20170712073556.h6tkpjcdzjaozozs@mwanda
Fixes: f0a3b154bd7 ("ftrace: Clarify code for mod command")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit c59f29cb144a6a0dfac16ede9dc8eafc02dc56ca upstream.
The 's' flag is supposed to indicate that a softirq is running. This
can be detected by testing the preempt_count with SOFTIRQ_OFFSET.
The current code tests the preempt_count with SOFTIRQ_MASK, which
would be true even when softirqs are disabled but not serving a
softirq.
Link: http://lkml.kernel.org/r/1481300417-3564-1-git-send-email-pkondeti@codeaurora.org
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 73bb059f9b8a00c5e1bf2f7ca83138c05d05e600 upstream.
The point of sched_group_mask is to select those CPUs from
sched_group_cpus that can actually arrive at this balance domain.
The current code gets it wrong, as can be readily demonstrated with a
topology like:
node 0 1 2 3
0: 10 20 30 20
1: 20 10 20 30
2: 30 20 10 20
3: 20 30 20 10
Where (for example) domain 1 on CPU1 ends up with a mask that includes
CPU0:
[] CPU1 attaching sched-domain:
[] domain 0: span 0-2 level NUMA
[] groups: 1 (mask: 1), 2, 0
[] domain 1: span 0-3 level NUMA
[] groups: 0-2 (mask: 0-2) (cpu_capacity: 3072), 0,2-3 (cpu_capacity: 3072)
This causes sched_balance_cpu() to compute the wrong CPU and
consequently should_we_balance() will terminate early resulting in
missed load-balance opportunities.
The fixed topology looks like:
[] CPU1 attaching sched-domain:
[] domain 0: span 0-2 level NUMA
[] groups: 1 (mask: 1), 2, 0
[] domain 1: span 0-3 level NUMA
[] groups: 0-2 (mask: 1) (cpu_capacity: 3072), 0,2-3 (cpu_capacity: 3072)
(note: this relies on OVERLAP domains to always have children, this is
true because the regular topology domains are still here -- this is
before degenerate trimming)
Debugged-by: Lauro Ramos Venancio <lvenanci@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: e3589f6c81e4 ("sched: Allow for overlapping sched_domain spans")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit f32d782e31bf079f600dcec126ed117b0577e85c upstream.
The group mask is always used in intersection with the group CPUs. So,
when building the group mask, we don't have to care about CPUs that are
not part of the group.
Signed-off-by: Lauro Ramos Venancio <lvenanci@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: lwang@redhat.com
Cc: riel@redhat.com
Link: http://lkml.kernel.org/r/1492717903-5195-2-git-send-email-lvenanci@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 0372dd2736e02672ac6e189c31f7d8c02ad543cd upstream.
When building the overlapping groups, we very obviously should start
with the previous domain of _this_ @cpu, not CPU-0.
This can be readily demonstrated with a topology like:
node 0 1 2 3
0: 10 20 30 20
1: 20 10 20 30
2: 30 20 10 20
3: 20 30 20 10
Where (for example) CPU1 ends up generating the following nonsensical groups:
[] CPU1 attaching sched-domain:
[] domain 0: span 0-2 level NUMA
[] groups: 1 2 0
[] domain 1: span 0-3 level NUMA
[] groups: 1-3 (cpu_capacity = 3072) 0-1,3 (cpu_capacity = 3072)
Where the fact that domain 1 doesn't include a group with span 0-2 is
the obvious fail.
With patch this looks like:
[] CPU1 attaching sched-domain:
[] domain 0: span 0-2 level NUMA
[] groups: 1 0 2
[] domain 1: span 0-3 level NUMA
[] groups: 0-2 (cpu_capacity = 3072) 0,2-3 (cpu_capacity = 3072)
Debugged-by: Lauro Ramos Venancio <lvenanci@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: e3589f6c81e4 ("sched: Allow for overlapping sched_domain spans")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit c6508a39640b9a27fc2bc10cb708152672c82045 upstream.
commit c743f0a5c50f2fcbc628526279cfa24f3dabe182 upstream.
More users for for_each_cpu_wrap() have appeared. Promote the construct
to generic cpumask interface.
The implementation is slightly modified to reduce arguments.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Lauro Ramos Venancio <lvenanci@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: lwang@redhat.com
Link: http://lkml.kernel.org/r/20170414122005.o35me2h5nowqkxbv@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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This reverts commit 1b568f0aabf280555125bc7cefc08321ff0ebaba.
For the 4.9 kernel tree, this patch causes scheduler regressions. It is
fixed in newer kernels with a large number of individual patches, the
sum of which is too big for the stable kernel tree.
Ingo recommended just reverting the single patch for this tree, as it's
much simpler.
Reported-by: Ben Guthro <ben@guthro.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 6b5fc3a1331810db407c9e0e673dc1837afdc9d0 upstream.
Wait/wakeup operations do not guarantee ordering on their own. Instead,
either locking or memory barriers are required. This commit therefore
adds memory barriers to wake_nocb_leader() and nocb_leader_wait().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Krister Johansen <kjlx@templeofstupid.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit c0d80ddab89916273cb97114889d3f337bc370ae upstream.
core_kernel_text is used by MIPS in its function graph trace processing,
so having this method traced leads to an infinite set of recursive calls
such as:
Call Trace:
ftrace_return_to_handler+0x50/0x128
core_kernel_text+0x10/0x1b8
prepare_ftrace_return+0x6c/0x114
ftrace_graph_caller+0x20/0x44
return_to_handler+0x10/0x30
return_to_handler+0x0/0x30
return_to_handler+0x0/0x30
ftrace_ops_no_ops+0x114/0x1bc
core_kernel_text+0x10/0x1b8
core_kernel_text+0x10/0x1b8
core_kernel_text+0x10/0x1b8
ftrace_ops_no_ops+0x114/0x1bc
core_kernel_text+0x10/0x1b8
prepare_ftrace_return+0x6c/0x114
ftrace_graph_caller+0x20/0x44
(...)
Mark the function notrace to avoid it being traced.
Link: http://lkml.kernel.org/r/1498028607-6765-1-git-send-email-marcin.nowakowski@imgtec.com
Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Meyer <thomas@m3y3r.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 6bdf6abc56b53103324dfd270a86580306e1a232 upstream.
Leaking kernel addresses on unpriviledged is generally disallowed,
for example, verifier rejects the following:
0: (b7) r0 = 0
1: (18) r2 = 0xffff897e82304400
3: (7b) *(u64 *)(r1 +48) = r2
R2 leaks addr into ctx
Doing pointer arithmetic on them is also forbidden, so that they
don't turn into unknown value and then get leaked out. However,
there's xadd as a special case, where we don't check the src reg
for being a pointer register, e.g. the following will pass:
0: (b7) r0 = 0
1: (7b) *(u64 *)(r1 +48) = r0
2: (18) r2 = 0xffff897e82304400 ; map
4: (db) lock *(u64 *)(r1 +48) += r2
5: (95) exit
We could store the pointer into skb->cb, loose the type context,
and then read it out from there again to leak it eventually out
of a map value. Or more easily in a different variant, too:
0: (bf) r6 = r1
1: (7a) *(u64 *)(r10 -8) = 0
2: (bf) r2 = r10
3: (07) r2 += -8
4: (18) r1 = 0x0
6: (85) call bpf_map_lookup_elem#1
7: (15) if r0 == 0x0 goto pc+3
R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R6=ctx R10=fp
8: (b7) r3 = 0
9: (7b) *(u64 *)(r0 +0) = r3
10: (db) lock *(u64 *)(r0 +0) += r6
11: (b7) r0 = 0
12: (95) exit
from 7 to 11: R0=inv,min_value=0,max_value=0 R6=ctx R10=fp
11: (b7) r0 = 0
12: (95) exit
Prevent this by checking xadd src reg for pointer types. Also
add a couple of test cases related to this.
Fixes: 1be7f75d1668 ("bpf: enable non-root eBPF programs")
Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit a0c4acd2c220376b4e9690e75782d0c0afdaab9f upstream.
If a writer could been woken up, the above branch
if (sem->count == 0)
break;
would have moved us to taking the sem. So, it's
not the time to wake a writer now, and only readers
are allowed now. Thus, 0 must be passed to __rwsem_do_wake().
Next, __rwsem_do_wake() wakes readers unconditionally.
But we mustn't do that if the sem is owned by writer
in the moment. Otherwise, writer and reader own the sem
the same time, which leads to memory corruption in
callers.
rwsem-xadd.c does not need that, as:
1) the similar check is made lockless there,
2) in __rwsem_mark_wake::try_reader_grant we test,
that sem is not owned by writer.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Niklas Cassel <niklas.cassel@axis.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 17fcbd590d0c "locking/rwsem: Fix down_write_killable() for CONFIG_RWSEM_GENERIC_SPINLOCK=y"
Link: http://lkml.kernel.org/r/149762063282.19811.9129615532201147826.stgit@localhost.localdomain
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 425fffd886bae3d127a08fa6a17f2e31e24ed7ff upstream.
Currently, inputting the following command will succeed but actually the
value will be truncated:
# echo 0x12ffffffff > /proc/sys/net/ipv4/tcp_notsent_lowat
This is not friendly to the user, so instead, we should report error
when the value is larger than UINT_MAX.
Fixes: e7d316a02f68 ("sysctl: handle error writing UINT_MAX to u32 fields")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Cc: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 5380e5644afbba9e3d229c36771134976f05c91e upstream.
I saw some very confusing sysctl output on my system:
# cat /proc/sys/net/core/xfrm_aevent_rseqth
-2
# cat /proc/sys/net/core/xfrm_aevent_etime
-10
# cat /proc/sys/net/ipv4/tcp_notsent_lowat
-4294967295
Because we forget to set the *negp flag in proc_douintvec, so it will
become a garbage value.
Since the value related to proc_douintvec is always an unsigned integer,
so we can set *negp to false explictily to fix this issue.
Fixes: e7d316a02f68 ("sysctl: handle error writing UINT_MAX to u32 fields")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Cc: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 9e52b32567126fe146f198971364f68d3bc5233f upstream.
Always try to parse an address, since kstrtoul() will safely fail when
given a symbol as input. If that fails (which will be the case for a
symbol), try to parse a symbol instead.
This allows creating a probe such as:
p:probe/vlan_gro_receive 8021q:vlan_gro_receive+0
Which is necessary for this command to work:
perf probe -m 8021q -a vlan_gro_receive
Link: http://lkml.kernel.org/r/fd72d666f45b114e2c5b9cf7e27b91de1ec966f1.1498122881.git.sd@queasysnail.net
Fixes: 413d37d1e ("tracing: Add kprobe-based event tracer")
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 6e5f32f7a43f45ee55c401c0b9585eb01f9629a8 upstream.
If we crossed a sample window while in NO_HZ we will add LOAD_FREQ to
the pending sample window time on exit, setting the next update not
one window into the future, but two.
This situation on exiting NO_HZ is described by:
this_rq->calc_load_update < jiffies < calc_load_update
In this scenario, what we should be doing is:
this_rq->calc_load_update = calc_load_update [ next window ]
But what we actually do is:
this_rq->calc_load_update = calc_load_update + LOAD_FREQ [ next+1 window ]
This has the effect of delaying load average updates for potentially
up to ~9seconds.
This can result in huge spikes in the load average values due to
per-cpu uninterruptible task counts being out of sync when accumulated
across all CPUs.
It's safe to update the per-cpu active count if we wake between sample
windows because any load that we left in 'calc_load_idle' will have
been zero'd when the idle load was folded in calc_global_load().
This issue is easy to reproduce before,
commit 9d89c257dfb9 ("sched/fair: Rewrite runnable load and utilization average tracking")
just by forking short-lived process pipelines built from ps(1) and
grep(1) in a loop. I'm unable to reproduce the spikes after that
commit, but the bug still seems to be present from code review.
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Fixes: commit 5167e8d ("sched/nohz: Rewrite and fix load-avg computation -- again")
Link: http://lkml.kernel.org/r/20170217120731.11868-2-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 63cae12bce9861cec309798d34701cf3da20bc71 ]
There is problem with installing an event in a task that is 'stuck' on
an offline CPU.
Blocked tasks are not dis-assosciated from offlined CPUs, after all, a
blocked task doesn't run and doesn't require a CPU etc.. Only on
wakeup do we ammend the situation and place the task on a available
CPU.
If we hit such a task with perf_install_in_context() we'll loop until
either that task wakes up or the CPU comes back online, if the task
waking depends on the event being installed, we're stuck.
While looking into this issue, I also spotted another problem, if we
hit a task with perf_install_in_context() that is in the middle of
being migrated, that is we observe the old CPU before sending the IPI,
but run the IPI (on the old CPU) while the task is already running on
the new CPU, things also go sideways.
Rework things to rely on task_curr() -- outside of rq->lock -- which
is rather tricky. Imagine the following scenario where we're trying to
install the first event into our task 't':
CPU0 CPU1 CPU2
(current == t)
t->perf_event_ctxp[] = ctx;
smp_mb();
cpu = task_cpu(t);
switch(t, n);
migrate(t, 2);
switch(p, t);
ctx = t->perf_event_ctxp[]; // must not be NULL
smp_function_call(cpu, ..);
generic_exec_single()
func();
spin_lock(ctx->lock);
if (task_curr(t)) // false
add_event_to_ctx();
spin_unlock(ctx->lock);
perf_event_context_sched_in();
spin_lock(ctx->lock);
// sees event
So its CPU0's store of t->perf_event_ctxp[] that must not go 'missing'.
Because if CPU2's load of that variable were to observe NULL, it would
not try to schedule the ctx and we'd have a task running without its
counter, which would be 'bad'.
As long as we observe !NULL, we'll acquire ctx->lock. If we acquire it
first and not see the event yet, then CPU0 must observe task_curr()
and retry. If the install happens first, then we must see the event on
sched-in and all is well.
I think we can translate the first part (until the 'must not be NULL')
of the scenario to a litmus test like:
C C-peterz
{
}
P0(int *x, int *y)
{
int r1;
WRITE_ONCE(*x, 1);
smp_mb();
r1 = READ_ONCE(*y);
}
P1(int *y, int *z)
{
WRITE_ONCE(*y, 1);
smp_store_release(z, 1);
}
P2(int *x, int *z)
{
int r1;
int r2;
r1 = smp_load_acquire(z);
smp_mb();
r2 = READ_ONCE(*x);
}
exists
(0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Where:
x is perf_event_ctxp[],
y is our tasks's CPU, and
z is our task being placed on the rq of CPU2.
The P0 smp_mb() is the one added by this patch, ordering the store to
perf_event_ctxp[] from find_get_context() and the load of task_cpu()
in task_function_call().
The smp_store_release/smp_load_acquire model the RCpc locking of the
rq->lock and the smp_mb() of P2 is the context switch switching from
whatever CPU2 was running to our task 't'.
This litmus test evaluates into:
Test C-peterz Allowed
States 7
0:r1=0; 2:r1=0; 2:r2=0;
0:r1=0; 2:r1=0; 2:r2=1;
0:r1=0; 2:r1=1; 2:r2=1;
0:r1=1; 2:r1=0; 2:r2=0;
0:r1=1; 2:r1=0; 2:r2=1;
0:r1=1; 2:r1=1; 2:r2=0;
0:r1=1; 2:r1=1; 2:r2=1;
No
Witnesses
Positive: 0 Negative: 7
Condition exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Observation C-peterz Never 0 7
Hash=e427f41d9146b2a5445101d3e2fcaa34
And the strong and weak model agree.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Will Deacon <will.deacon@arm.com>
Cc: jeremy.linton@arm.com
Link: http://lkml.kernel.org/r/20161209135900.GU3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit ff7a28a074ccbea999dadbb58c46212cf90984c6 ]
When a system panics, the "Rebooting in X seconds.." message is never
printed because it lacks a new line. Fix it.
Link: http://lkml.kernel.org/r/20170119114751.2724-1-jslaby@suse.cz
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit d407bd25a204bd66b7346dde24bd3d37ef0e0b05 ]
This patch adds two helpers, bpf_map_area_alloc() and bpf_map_area_free(),
that are to be used for map allocations. Using kmalloc() for very large
allocations can cause excessive work within the page allocator, so i) fall
back earlier to vmalloc() when the attempt is considered costly anyway,
and even more importantly ii) don't trigger OOM killer with any of the
allocators.
Since this is based on a user space request, for example, when creating
maps with element pre-allocation, we really want such requests to fail
instead of killing other user space processes.
Also, don't spam the kernel log with warnings should any of the allocations
fail under pressure. Given that, we can make backend selection in
bpf_map_area_alloc() generic, and convert all maps over to use this API
for spots with potentially large allocation requests.
Note, replacing the one kmalloc_array() is fine as overflow checks happen
earlier in htab_map_alloc(), since it must also protect the multiplication
for vmalloc() should kmalloc_array() fail.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 3d88d56c5873f6eebe23e05c3da701960146b801 upstream.
Due to how the MONOTONIC_RAW accumulation logic was handled,
there is the potential for a 1ns discontinuity when we do
accumulations. This small discontinuity has for the most part
gone un-noticed, but since ARM64 enabled CLOCK_MONOTONIC_RAW
in their vDSO clock_gettime implementation, we've seen failures
with the inconsistency-check test in kselftest.
This patch addresses the issue by using the same sub-ns
accumulation handling that CLOCK_MONOTONIC uses, which avoids
the issue for in-kernel users.
Since the ARM64 vDSO implementation has its own clock_gettime
calculation logic, this patch reduces the frequency of errors,
but failures are still seen. The ARM64 vDSO will need to be
updated to include the sub-nanosecond xtime_nsec values in its
calculation for this issue to be completely fixed.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Tested-by: Daniel Mentz <danielmentz@google.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Link: http://lkml.kernel.org/r/1496965462-20003-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit ceea5e3771ed2378668455fa21861bead7504df5 upstream.
In tests, which excercise switching of clocksources, a NULL
pointer dereference can be observed on AMR64 platforms in the
clocksource read() function:
u64 clocksource_mmio_readl_down(struct clocksource *c)
{
return ~(u64)readl_relaxed(to_mmio_clksrc(c)->reg) & c->mask;
}
This is called from the core timekeeping code via:
cycle_now = tkr->read(tkr->clock);
tkr->read is the cached tkr->clock->read() function pointer.
When the clocksource is changed then tkr->clock and tkr->read
are updated sequentially. The code above results in a sequential
load operation of tkr->read and tkr->clock as well.
If the store to tkr->clock hits between the loads of tkr->read
and tkr->clock, then the old read() function is called with the
new clock pointer. As a consequence the read() function
dereferences a different data structure and the resulting 'reg'
pointer can point anywhere including NULL.
This problem was introduced when the timekeeping code was
switched over to use struct tk_read_base. Before that, it was
theoretically possible as well when the compiler decided to
reload clock in the code sequence:
now = tk->clock->read(tk->clock);
Add a helper function which avoids the issue by reading
tk_read_base->clock once into a local variable clk and then issue
the read function via clk->read(clk). This guarantees that the
read() function always gets the proper clocksource pointer handed
in.
Since there is now no use for the tkr.read pointer, this patch
also removes it, and to address stopping the fast timekeeper
during suspend/resume, it introduces a dummy clocksource to use
rather then just a dummy read function.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Daniel Mentz <danielmentz@google.com>
Link: http://lkml.kernel.org/r/1496965462-20003-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 57db7e4a2d92c2d3dfbca4ef8057849b2682436b upstream.
Thomas Gleixner wrote:
> The CRIU support added a 'feature' which allows a user space task to send
> arbitrary (kernel) signals to itself. The changelog says:
>
> The kernel prevents sending of siginfo with positive si_code, because
> these codes are reserved for kernel. I think we can allow a task to
> send such a siginfo to itself. This operation should not be dangerous.
>
> Quite contrary to that claim, it turns out that it is outright dangerous
> for signals with info->si_code == SI_TIMER. The following code sequence in
> a user space task allows to crash the kernel:
>
> id = timer_create(CLOCK_XXX, ..... signo = SIGX);
> timer_set(id, ....);
> info->si_signo = SIGX;
> info->si_code = SI_TIMER:
> info->_sifields._timer._tid = id;
> info->_sifields._timer._sys_private = 2;
> rt_[tg]sigqueueinfo(..., SIGX, info);
> sigemptyset(&sigset);
> sigaddset(&sigset, SIGX);
> rt_sigtimedwait(sigset, info);
>
> For timers based on CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID this
> results in a kernel crash because sigwait() dequeues the signal and the
> dequeue code observes:
>
> info->si_code == SI_TIMER && info->_sifields._timer._sys_private != 0
>
> which triggers the following callchain:
>
> do_schedule_next_timer() -> posix_cpu_timer_schedule() -> arm_timer()
>
> arm_timer() executes a list_add() on the timer, which is already armed via
> the timer_set() syscall. That's a double list add which corrupts the posix
> cpu timer list. As a consequence the kernel crashes on the next operation
> touching the posix cpu timer list.
>
> Posix clocks which are internally implemented based on hrtimers are not
> affected by this because hrtimer_start() can handle already armed timers
> nicely, but it's a reliable way to trigger the WARN_ON() in
> hrtimer_forward(), which complains about calling that function on an
> already armed timer.
This problem has existed since the posix timer code was merged into
2.5.63. A few releases earlier in 2.5.60 ptrace gained the ability to
inject not just a signal (which linux has supported since 1.0) but the
full siginfo of a signal.
The core problem is that the code will reschedule in response to
signals getting dequeued not just for signals the timers sent but
for other signals that happen to a si_code of SI_TIMER.
Avoid this confusion by testing to see if the queued signal was
preallocated as all timer signals are preallocated, and so far
only the timer code preallocates signals.
Move the check for if a timer needs to be rescheduled up into
collect_signal where the preallocation check must be performed,
and pass the result back to dequeue_signal where the code reschedules
timers. This makes it clear why the code cares about preallocated
timers.
Reported-by: Thomas Gleixner <tglx@linutronix.de>
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Reference: 66dd34ad31e5 ("signal: allow to send any siginfo to itself")
Reference: 1669ce53e2ff ("Add PTRACE_GETSIGINFO and PTRACE_SETSIGINFO")
Fixes: db8b50ba75f2 ("[PATCH] POSIX clocks & timers")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit ff86bf0c65f14346bf2440534f9ba5ac232c39a0 upstream.
The alarmtimer code has another source of potentially rearming itself too
fast. Interval timers with a very samll interval have a similar CPU hog
effect as the previously fixed overflow issue.
The reason is that alarmtimers do not implement the normal protection
against this kind of problem which the other posix timer use:
timer expires -> queue signal -> deliver signal -> rearm timer
This scheme brings the rearming under scheduler control and prevents
permanently firing timers which hog the CPU.
Bringing this scheme to the alarm timer code is a major overhaul because it
lacks all the necessary mechanisms completely.
So for a quick fix limit the interval to one jiffie. This is not
problematic in practice as alarmtimers are usually backed by an RTC for
suspend which have 1 second resolution. It could be therefor argued that
the resolution of this clock should be set to 1 second in general, but
that's outside the scope of this fix.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kostya Serebryany <kcc@google.com>
Cc: syzkaller <syzkaller@googlegroups.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Link: http://lkml.kernel.org/r/20170530211655.896767100@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit f4781e76f90df7aec400635d73ea4c35ee1d4765 upstream.
Andrey reported a alartimer related RCU stall while fuzzing the kernel with
syzkaller.
The reason for this is an overflow in ktime_add() which brings the
resulting time into negative space and causes immediate expiry of the
timer. The following rearm with a small interval does not bring the timer
back into positive space due to the same issue.
This results in a permanent firing alarmtimer which hogs the CPU.
Use ktime_add_safe() instead which detects the overflow and clamps the
result to KTIME_SEC_MAX.
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kostya Serebryany <kcc@google.com>
Cc: syzkaller <syzkaller@googlegroups.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Link: http://lkml.kernel.org/r/20170530211655.802921648@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit fa07ab72cbb0d843429e61bf179308aed6cbe0dd upstream.
In case __irq_set_trigger() fails the resources requested via
irq_request_resources() are not released.
Add the missing release call into the error handling path.
Fixes: c1bacbae8192 ("genirq: Provide irq_request/release_resources chip callbacks")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/655538f5-cb20-a892-ff15-fbd2dd1fa4ec@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 252d2a4117bc181b287eeddf848863788da733ae upstream.
idle_task_exit() can be called with IRQs on x86 on and therefore
should use switch_mm(), not switch_mm_irqs_off().
This doesn't seem to cause any problems right now, but it will
confuse my upcoming TLB flush changes. Nonetheless, I think it
should be backported because it's trivial. There won't be any
meaningful performance impact because idle_task_exit() is only
used when offlining a CPU.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: f98db6013c55 ("sched/core: Add switch_mm_irqs_off() and use it in the scheduler")
Link: http://lkml.kernel.org/r/ca3d1a9fa93a0b49f5a8ff729eda3640fb6abdf9.1497034141.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit b94f51183b0617e7b9b4fb4137d4cf1cab7547c2 ]
On an overloaded system, it is possible that a change in the watchdog
threshold can be delayed long enough to trigger a false positive.
This can easily be achieved by having a cpu spinning indefinitely on a
task, while another cpu updates watchdog threshold.
What happens is while trying to park the watchdog threads, the hrtimers
on the other cpus trigger and reprogram themselves with the new slower
watchdog threshold. Meanwhile, the nmi watchdog is still programmed
with the old faster threshold.
Because the one cpu is blocked, it prevents the thread parking on the
other cpus from completing, which is needed to shutdown the nmi watchdog
and reprogram it correctly. As a result, a false positive from the nmi
watchdog is reported.
Fix this by setting a park_in_progress flag to block all lockups until
the parking is complete.
Fix provided by Ulrich Obergfell.
[akpm@linux-foundation.org: s/park_in_progress/watchdog_park_in_progress/]
Link: http://lkml.kernel.org/r/1481041033-192236-1-git-send-email-dzickus@redhat.com
Signed-off-by: Don Zickus <dzickus@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 249e52e35580fcfe5dad53a7dcd7c1252788749c ]
Patch series "Clean up watchdog handlers", v2.
This is an attempt to cleanup watchdog handlers. Right now,
kernel/watchdog.c implements both softlockup and hardlockup detectors.
Softlockup code is generic. Hardlockup code is arch specific. Some
architectures don't use hardlockup detectors. They use their own
watchdog detectors. To make both these combination work, we have
numerous #ifdefs in kernel/watchdog.c.
We are trying here to make these handlers independent of each other.
Also provide an interface for architectures to implement their own
handlers. watchdog_nmi_enable and watchdog_nmi_disable will be defined
as weak such that architectures can override its definitions.
Thanks to Don Zickus for his suggestions.
Here are our previous discussions
http://www.spinics.net/lists/sparclinux/msg16543.html
http://www.spinics.net/lists/sparclinux/msg16441.html
This patch (of 3):
Move shared macros and definitions to nmi.h so that watchdog.c, new file
watchdog_hld.c or any other architecture specific handler can use those
definitions.
Link: http://lkml.kernel.org/r/1478034826-43888-2-git-send-email-babu.moger@oracle.com
Signed-off-by: Babu Moger <babu.moger@oracle.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Josh Hunt <johunt@akamai.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 73ce0511c43686095efd2f65ef564aab952e07bc ]
Separate hardlockup code from watchdog.c and move it to watchdog_hld.c.
It is mostly straight forward. Remove everything inside
CONFIG_HARDLOCKUP_DETECTORS. This code will go to file watchdog_hld.c.
Also update the makefile accordigly.
Link: http://lkml.kernel.org/r/1478034826-43888-3-git-send-email-babu.moger@oracle.com
Signed-off-by: Babu Moger <babu.moger@oracle.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Josh Hunt <johunt@akamai.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit ed5bd7dc88edf4a4a9c67130742b1b59aa017a5f ]
The user_header gets caught by kmemleak with the following splat as
missing a free:
unreferenced object 0xffff99667a733d80 (size 96):
comm "swapper/0", pid 1, jiffies 4294892317 (age 62191.468s)
hex dump (first 32 bytes):
a0 b6 92 b4 ff ff ff ff 00 00 00 00 01 00 00 00 ................
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
kmemleak_alloc+0x4a/0xa0
__kmalloc+0x144/0x260
__register_sysctl_table+0x54/0x5e0
register_sysctl+0x1b/0x20
user_namespace_sysctl_init+0x17/0x34
do_one_initcall+0x52/0x1a0
kernel_init_freeable+0x173/0x200
kernel_init+0xe/0x100
ret_from_fork+0x2c/0x40
The BUG_ON()s are intended to crash so no need to clean up after
ourselves on error there. This is also a kernel/ subsys_init() we don't
need a respective exit call here as this is never modular, so just white
list it.
Link: http://lkml.kernel.org/r/20170203211404.31458-1-mcgrof@kernel.org
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Nikolay Borisov <n.borisov.lkml@gmail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 4296f23ed49a15d36949458adcc66ff993dee2a8 upstream.
sugov_start() only initializes struct sugov_cpu per-CPU structures
for shared policies, but it should do that for single-CPU policies too.
That in particular makes the IO-wait boost mechanism work in the
cases when cpufreq policies correspond to individual CPUs.
Fixes: 21ca6d2c52f8 (cpufreq: schedutil: Add iowait boosting)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 6c4f0fa643cb9e775dcc976e3db00d649468ff1d upstream.
cached_raw_freq applies to the entire cpufreq policy and not individual
CPUs. Apart from wasting per-cpu memory, it is actually wrong to keep it
in struct sugov_cpu as we may end up comparing next_freq with a stale
cached_raw_freq of a random CPU.
Move cached_raw_freq to struct sugov_policy.
Fixes: 5cbea46984d6 (cpufreq: schedutil: map raw required frequency to driver frequency)
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 40da1b11f01e43aad1aa6cea64681b6125e8a2a7 upstream.
If a custom CPU target is specified and that one is not available _or_
can't be interrupted then the code returns to userland without dropping a
lock as notices by lockdep:
|echo 133 > /sys/devices/system/cpu/cpu7/hotplug/target
| ================================================
| [ BUG: lock held when returning to user space! ]
| ------------------------------------------------
| bash/503 is leaving the kernel with locks still held!
| 1 lock held by bash/503:
| #0: (device_hotplug_lock){+.+...}, at: [<ffffffff815b5650>] lock_device_hotplug_sysfs+0x10/0x40
So release the lock then.
Fixes: 757c989b9994 ("cpu/hotplug: Make target state writeable")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170602142714.3ogo25f2wbq6fjpj@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit cc1582c231ea041fbc68861dfaf957eaf902b829 upstream.
When doing sampling, for example:
perf record -e cycles:u ...
On workloads that do a lot of kernel entry/exits we see kernel
samples, even though :u is specified. This is due to skid existing.
This might be a security issue because it can leak kernel addresses even
though kernel sampling support is disabled.
The patch drops the kernel samples if exclude_kernel is specified.
For example, test on Haswell desktop:
perf record -e cycles:u <mgen>
perf report --stdio
Before patch applied:
99.77% mgen mgen [.] buf_read
0.20% mgen mgen [.] rand_buf_init
0.01% mgen [kernel.vmlinux] [k] apic_timer_interrupt
0.00% mgen mgen [.] last_free_elem
0.00% mgen libc-2.23.so [.] __random_r
0.00% mgen libc-2.23.so [.] _int_malloc
0.00% mgen mgen [.] rand_array_init
0.00% mgen [kernel.vmlinux] [k] page_fault
0.00% mgen libc-2.23.so [.] __random
0.00% mgen libc-2.23.so [.] __strcasestr
0.00% mgen ld-2.23.so [.] strcmp
0.00% mgen ld-2.23.so [.] _dl_start
0.00% mgen libc-2.23.so [.] sched_setaffinity@@GLIBC_2.3.4
0.00% mgen ld-2.23.so [.] _start
We can see kernel symbols apic_timer_interrupt and page_fault.
After patch applied:
99.79% mgen mgen [.] buf_read
0.19% mgen mgen [.] rand_buf_init
0.00% mgen libc-2.23.so [.] __random_r
0.00% mgen mgen [.] rand_array_init
0.00% mgen mgen [.] last_free_elem
0.00% mgen libc-2.23.so [.] vfprintf
0.00% mgen libc-2.23.so [.] rand
0.00% mgen libc-2.23.so [.] __random
0.00% mgen libc-2.23.so [.] _int_malloc
0.00% mgen libc-2.23.so [.] _IO_doallocbuf
0.00% mgen ld-2.23.so [.] do_lookup_x
0.00% mgen ld-2.23.so [.] open_verify.constprop.7
0.00% mgen ld-2.23.so [.] _dl_important_hwcaps
0.00% mgen libc-2.23.so [.] sched_setaffinity@@GLIBC_2.3.4
0.00% mgen ld-2.23.so [.] _start
There are only userspace symbols.
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: acme@kernel.org
Cc: jolsa@kernel.org
Cc: kan.liang@intel.com
Cc: mark.rutland@arm.com
Cc: will.deacon@arm.com
Cc: yao.jin@intel.com
Link: http://lkml.kernel.org/r/1495706947-3744-1-git-send-email-yao.jin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 41c25707d21716826e3c1f60967f5550610ec1c9 upstream.
In most cases, a cgroup controller don't care about the liftimes of
cgroups. For the controller, a css becomes online when ->css_online()
is called on it and offline when ->css_offline() is called.
However, cpuset is special in that the user interface it exposes cares
whether certain cgroups exist or not. Combined with the RCU delay
between cgroup removal and css offlining, this can lead to user
visible behavior oddities where operations which should succeed after
cgroup removals fail for some time period. The effects of cgroup
removals are delayed when seen from userland.
This patch adds css_is_dying() which tests whether offline is pending
and updates is_cpuset_online() so that the function returns false also
while offline is pending. This gets rid of the userland visible
delays.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Link: http://lkml.kernel.org/r/327ca1f5-7957-fbb9-9e5f-9ba149d40ba2@oracle.com
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 33c35aa4817864e056fd772230b0c6b552e36ea2 upstream.
The kill_css() function may be called more than once under the condition
that the css was killed but not physically removed yet followed by the
removal of the cgroup that is hosting the css. This patch prevents any
harmm from being done when that happens.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit c70d9d809fdeecedb96972457ee45c49a232d97f upstream.
When I introduced ptracer_cred I failed to consider the weirdness of
fork where the task_struct copies the old value by default. This
winds up leaving ptracer_cred set even when a process forks and
the child process does not wind up being ptraced.
Because ptracer_cred is not set on non-ptraced processes whose
parents were ptraced this has broken the ability of the enlightenment
window manager to start setuid children.
Fix this by properly initializing ptracer_cred in ptrace_init_task
This must be done with a little bit of care to preserve the current value
of ptracer_cred when ptrace carries through fork. Re-reading the
ptracer_cred from the ptracing process at this point is inconsistent
with how PT_PTRACE_CAP has been maintained all of these years.
Tested-by: Takashi Iwai <tiwai@suse.de>
Fixes: 64b875f7ac8a ("ptrace: Capture the ptracer's creds not PT_PTRACE_CAP")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 30e7d894c1478c88d50ce94ddcdbd7f9763d9cdd upstream.
Enabling the tracer selftest triggers occasionally the warning in
text_poke(), which warns when the to be modified page is not marked
reserved.
The reason is that the tracer selftest installs kprobes on functions marked
__init for testing. These probes are removed after the tests, but that
removal schedules the delayed kprobes_optimizer work, which will do the
actual text poke. If the work is executed after the init text is freed,
then the warning triggers. The bug can be reproduced reliably when the work
delay is increased.
Flush the optimizer work and wait for the optimizing/unoptimizing lists to
become empty before returning from the kprobes tracer selftest. That
ensures that all operations which were queued due to the probes removal
have completed.
Link: http://lkml.kernel.org/r/20170516094802.76a468bb@gandalf.local.home
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 6274de498 ("kprobes: Support delayed unoptimizing")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 2c4569ca26986d18243f282dd727da27e9adae4c upstream.
irq_set_chained_handler_and_data() sets up the chained interrupt and then
stores the handler data.
That's racy against an immediate interrupt which gets handled before the
store of the handler data happened. The handler will dereference a NULL
pointer and crash.
Cure it by storing handler data before installing the chained handler.
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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bits to 64 bits on 64-bit platforms
commit 5ea30e4e58040cfd6434c2f33dc3ea76e2c15b05 upstream.
The stack canary is an 'unsigned long' and should be fully initialized to
random data rather than only 32 bits of random data.
Signed-off-by: Daniel Micay <danielmicay@gmail.com>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Arjan van Ven <arjan@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-hardening@lists.openwall.com
Link: http://lkml.kernel.org/r/20170504133209.3053-1-danielmicay@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 3fd37226216620c1a468afa999739d5016fbc349 upstream.
Imagine we have a pid namespace and a task from its parent's pid_ns,
which made setns() to the pid namespace. The task is doing fork(),
while the pid namespace's child reaper is dying. We have the race
between them:
Task from parent pid_ns Child reaper
copy_process() ..
alloc_pid() ..
.. zap_pid_ns_processes()
.. disable_pid_allocation()
.. read_lock(&tasklist_lock)
.. iterate over pids in pid_ns
.. kill tasks linked to pids
.. read_unlock(&tasklist_lock)
write_lock_irq(&tasklist_lock); ..
attach_pid(p, PIDTYPE_PID); ..
.. ..
So, just created task p won't receive SIGKILL signal,
and the pid namespace will be in contradictory state.
Only manual kill will help there, but does the userspace
care about this? I suppose, the most users just inject
a task into a pid namespace and wait a SIGCHLD from it.
The patch fixes the problem. It simply checks for
(pid_ns->nr_hashed & PIDNS_HASH_ADDING) in copy_process().
We do it under the tasklist_lock, and can't skip
PIDNS_HASH_ADDING as noted by Oleg:
"zap_pid_ns_processes() does disable_pid_allocation()
and then takes tasklist_lock to kill the whole namespace.
Given that copy_process() checks PIDNS_HASH_ADDING
under write_lock(tasklist) they can't race;
if copy_process() takes this lock first, the new child will
be killed, otherwise copy_process() can't miss
the change in ->nr_hashed."
If allocation is disabled, we just return -ENOMEM
like it's made for such cases in alloc_pid().
v2: Do not move disable_pid_allocation(), do not
introduce a new variable in copy_process() and simplify
the patch as suggested by Oleg Nesterov.
Account the problem with double irq enabling
found by Eric W. Biederman.
Fixes: c876ad768215 ("pidns: Stop pid allocation when init dies")
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Ingo Molnar <mingo@kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Mike Rapoport <rppt@linux.vnet.ibm.com>
CC: Michal Hocko <mhocko@suse.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: "Eric W. Biederman" <ebiederm@xmission.com>
CC: Andrei Vagin <avagin@openvz.org>
CC: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Serge Hallyn <serge@hallyn.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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