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| author | Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> | 2019-02-01 14:21:08 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-02-01 15:46:23 -0800 |
| commit | 6376360ecbe525a9c17b3d081dfd88ba3e4ed65b (patch) | |
| tree | 215bed178518c6a6ecf4005927c3f598105cb3dc /mm | |
| parent | 0d0c8de8788b6c441ea01365612de7efc20cc682 (diff) | |
| download | lwn-6376360ecbe525a9c17b3d081dfd88ba3e4ed65b.tar.gz lwn-6376360ecbe525a9c17b3d081dfd88ba3e4ed65b.zip | |
mm: hwpoison: use do_send_sig_info() instead of force_sig()
Currently memory_failure() is racy against process's exiting, which
results in kernel crash by null pointer dereference.
The root cause is that memory_failure() uses force_sig() to forcibly
kill asynchronous (meaning not in the current context) processes. As
discussed in thread https://lkml.org/lkml/2010/6/8/236 years ago for OOM
fixes, this is not a right thing to do. OOM solves this issue by using
do_send_sig_info() as done in commit d2d393099de2 ("signal:
oom_kill_task: use SEND_SIG_FORCED instead of force_sig()"), so this
patch is suggesting to do the same for hwpoison. do_send_sig_info()
properly accesses to siglock with lock_task_sighand(), so is free from
the reported race.
I confirmed that the reported bug reproduces with inserting some delay
in kill_procs(), and it never reproduces with this patch.
Note that memory_failure() can send another type of signal using
force_sig_mceerr(), and the reported race shouldn't happen on it because
force_sig_mceerr() is called only for synchronous processes (i.e.
BUS_MCEERR_AR happens only when some process accesses to the corrupted
memory.)
Link: http://lkml.kernel.org/r/20190116093046.GA29835@hori1.linux.bs1.fc.nec.co.jp
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memory-failure.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 7c72f2a95785..831be5ff5f4d 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -372,7 +372,8 @@ static void kill_procs(struct list_head *to_kill, int forcekill, bool fail, if (fail || tk->addr_valid == 0) { pr_err("Memory failure: %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n", pfn, tk->tsk->comm, tk->tsk->pid); - force_sig(SIGKILL, tk->tsk); + do_send_sig_info(SIGKILL, SEND_SIG_PRIV, + tk->tsk, PIDTYPE_PID); } /* |