From c7b6a566b98524baea6a244186e665d22b633545 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Tue, 7 Apr 2020 21:40:10 -0400 Subject: 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: 71335f37c5e8 ("mm/gup: allow to react to fatal signals") Reported-by: syzbot+a8c70b7f3579fc0587dc@syzkaller.appspotmail.com Signed-off-by: Peter Xu Signed-off-by: Linus Torvalds --- mm/gup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/gup.c b/mm/gup.c index a21230569520..afce0bc47e70 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -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) { -- cgit v1.2.3