The patch titled
Subject: mm: check for SIGKILL inside dup_mmap() loop.
has been added to the -mm tree. Its filename is
mm-check-for-sigkill-inside-dup_mmap-loop.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-check-for-sigkill-inside-dup_mmap-loop.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-check-for-sigkill-inside-dup_mmap-loop.patch
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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: mm: check for SIGKILL inside dup_mmap() loop.
As a theoretical problem, dup_mmap() of an mm_struct with 60000+ vmas can
loop while potentially allocating memory, with mm->mmap_sem held for write
by current thread. This is bad if current thread was selected as an OOM
victim, for current thread will continue allocations using memory reserves
while OOM reaper is unable to reclaim memory.
As an actually observable problem, it is not difficult to make OOM reaper
unable to reclaim memory if the OOM victim is blocked at
i_mmap_lock_write() in this loop. Unfortunately, since nobody can explain
whether it is safe to use killable wait there, let's check for SIGKILL
before trying to allocate memory. Even without an OOM event, there is no
point with continuing the loop from the beginning if current thread is
killed.
Link: http://lkml.kernel.org/r/201804071938.CDE04681.SOFVQJFtMHOOLF@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 4 ++++
1 file changed, 4 insertions(+)
diff -puN kernel/fork.c~mm-check-for-sigkill-inside-dup_mmap-loop kernel/fork.c
--- a/kernel/fork.c~mm-check-for-sigkill-inside-dup_mmap-loop
+++ a/kernel/fork.c
@@ -440,6 +440,10 @@ static __latent_entropy int dup_mmap(str
continue;
}
charge = 0;
+ if (fatal_signal_pending(current)) {
+ retval = -EINTR;
+ goto out;
+ }
if (mpnt->vm_flags & VM_ACCOUNT) {
unsigned long len = vma_pages(mpnt);
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
fs-elf-dont-complain-map_fixed_noreplace-unless-eexist-error.patch
dentry-fix-kmemcheck-splat-at-take_dentry_name_snapshot.patch
mm-check-for-sigkill-inside-dup_mmap-loop.patch
mmvmscan-mark-register_shrinker-as-__must_check.patch
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