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mm/gup: Mark lock taken only after a successful retake

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It's definitely incorrect to mark the lock as taken even if
down_read_killable() failed.

This wass overlooked when we switched from down_read() to
down_read_killable() because down_read() won't fail while
down_read_killable() could.

Fixes: 71335f37c5 ("mm/gup: allow to react to fatal signals")
Reported-by: syzbot+a8c70b7f3579fc0587dc@syzkaller.appspotmail.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Xu 2020-04-07 21:40:10 -04:00 committed by Linus Torvalds
parent ba841078cd
commit c7b6a566b9
1 changed files with 1 additions and 1 deletions
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2
mm/gup.c
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@ -1329,7 +1329,6 @@ retry:
if (fatal_signal_pending(current))
break;
*locked = 1;
ret = down_read_killable(&mm->mmap_sem);
if (ret) {
BUG_ON(ret > 0);
@ -1338,6 +1337,7 @@ retry:
break;
}
*locked = 1;
ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
pages, NULL, locked);
if (!*locked) {