Commit c7b6a566 authored Apr 07, 2020 by Peter Xu Committed by Linus Torvalds Apr 07, 2020

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



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: 71335f37 ("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>

parent ba841078

mm/gup.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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) {

Admin message