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| author | Leon Yu <chianglungyu@gmail.com> | 2016-10-28 00:46:50 (GMT) |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-28 01:43:43 (GMT) |
| commit | 06b2849d103f4a91212876a211d0d7df227a9513 (patch) | |
| tree | de0cb888759169d999054497f35faa8f06b4765e | |
| parent | 37df49f433bc3a11f5716fe65aaec5189c6402cb (diff) | |
| download | linux-06b2849d103f4a91212876a211d0d7df227a9513.tar.xz | |
proc: fix NULL dereference when reading /proc/<pid>/auxv
Reading auxv of any kernel thread results in NULL pointer dereferencing
in auxv_read() where mm can be NULL. Fix that by checking for NULL mm
and bailing out early. This is also the original behavior changed by
recent commit c5317167854e ("proc: switch auxv to use of __mem_open()").
# cat /proc/2/auxv
Unable to handle kernel NULL pointer dereference at virtual address 000000a8
Internal error: Oops: 17 [#1] PREEMPT SMP ARM
CPU: 3 PID: 113 Comm: cat Not tainted 4.9.0-rc1-ARCH+ #1
Hardware name: BCM2709
task: ea3b0b00 task.stack: e99b2000
PC is at auxv_read+0x24/0x4c
LR is at do_readv_writev+0x2fc/0x37c
Process cat (pid: 113, stack limit = 0xe99b2210)
Call chain:
auxv_read
do_readv_writev
vfs_readv
default_file_splice_read
splice_direct_to_actor
do_splice_direct
do_sendfile
SyS_sendfile64
ret_fast_syscall
Fixes: c5317167854e ("proc: switch auxv to use of __mem_open()")
Link: http://lkml.kernel.org/r/1476966200-14457-1-git-send-email-chianglungyu@gmail.com
Signed-off-by: Leon Yu <chianglungyu@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Janis Danisevskis <jdanis@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/proc/base.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index adfc5b4..ca651ac 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1012,6 +1012,9 @@ static ssize_t auxv_read(struct file *file, char __user *buf, { struct mm_struct *mm = file->private_data; unsigned int nwords = 0; + + if (!mm) + return 0; do { nwords += 2; } while (mm->saved_auxv[nwords - 2] != 0); /* AT_NULL */ |