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authorLeon Yu <chianglungyu@gmail.com>2016-10-28 02:46:50 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-28 03:43:43 +0200
commit06b2849d103f4a91212876a211d0d7df227a9513 (patch)
treede0cb888759169d999054497f35faa8f06b4765e /fs/proc
parentmm: kmemleak: ensure that the task stack is not freed during scanning (diff)
downloadlinux-06b2849d103f4a91212876a211d0d7df227a9513.tar.xz
linux-06b2849d103f4a91212876a211d0d7df227a9513.zip
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>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/base.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index adfc5b4986f5..ca651ac00660 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 */