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author | Namhyung Kim <namhyung@kernel.org> | 2017-04-17 02:44:27 (GMT) |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-04-21 07:31:22 (GMT) |
commit | 7da0f8e547c2d3cac939da24458a88cce550af11 (patch) | |
tree | 9083bebc537667c9542b59000847699a9a356754 /kernel/trace/ftrace.c | |
parent | e3c7258bb4fe5b509621ce643f096502dceec8a4 (diff) | |
download | linux-7da0f8e547c2d3cac939da24458a88cce550af11.tar.xz |
ftrace: Fix function pid filter on instances
commit d879d0b8c183aabeb9a65eba91f3f9e3c7e7b905 upstream.
When function tracer has a pid filter, it adds a probe to sched_switch
to track if current task can be ignored. The probe checks the
ftrace_ignore_pid from current tr to filter tasks. But it misses to
delete the probe when removing an instance so that it can cause a crash
due to the invalid tr pointer (use-after-free).
This is easily reproducible with the following:
# cd /sys/kernel/debug/tracing
# mkdir instances/buggy
# echo $$ > instances/buggy/set_ftrace_pid
# rmdir instances/buggy
============================================================================
BUG: KASAN: use-after-free in ftrace_filter_pid_sched_switch_probe+0x3d/0x90
Read of size 8 by task kworker/0:1/17
CPU: 0 PID: 17 Comm: kworker/0:1 Tainted: G B 4.11.0-rc3 #198
Call Trace:
dump_stack+0x68/0x9f
kasan_object_err+0x21/0x70
kasan_report.part.1+0x22b/0x500
? ftrace_filter_pid_sched_switch_probe+0x3d/0x90
kasan_report+0x25/0x30
__asan_load8+0x5e/0x70
ftrace_filter_pid_sched_switch_probe+0x3d/0x90
? fpid_start+0x130/0x130
__schedule+0x571/0xce0
...
To fix it, use ftrace_clear_pids() to unregister the probe. As
instance_rmdir() already updated ftrace codes, it can just free the
filter safely.
Link: http://lkml.kernel.org/r/20170417024430.21194-2-namhyung@kernel.org
Fixes: 0c8916c34203 ("tracing: Add rmdir to remove multibuffer instances")
Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/trace/ftrace.c')
-rw-r--r-- | kernel/trace/ftrace.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 3bd975c..221eb59 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5401,6 +5401,15 @@ static void clear_ftrace_pids(struct trace_array *tr) trace_free_pid_list(pid_list); } +void ftrace_clear_pids(struct trace_array *tr) +{ + mutex_lock(&ftrace_lock); + + clear_ftrace_pids(tr); + + mutex_unlock(&ftrace_lock); +} + static void ftrace_pid_reset(struct trace_array *tr) { mutex_lock(&ftrace_lock); |