path: root/mm/memory-failure.c
diff options
authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>2019-02-01 14:21:08 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-02-01 15:46:23 -0800
commit6376360ecbe525a9c17b3d081dfd88ba3e4ed65b (patch)
tree215bed178518c6a6ecf4005927c3f598105cb3dc /mm/memory-failure.c
parentkasan: mark file common so ftrace doesn't trace it (diff)
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 '')
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);