From 79349abdcc3422ba50e2596a1a26b2a5967eb44a Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Tue, 7 Apr 2020 21:40:10 -0400 Subject: [PATCH] UPSTREAM: 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 (cherry picked from commit c7b6a566b98524baea6a244186e665d22b633545) Bug: 176847924 Signed-off-by: Kalesh Singh Change-Id: Id0e1fe147e87ff6bba02d5e590f6346089c5e650 --- mm/gup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/gup.c b/mm/gup.c index 02db28677fab..2c490384b9a8 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1099,7 +1099,6 @@ retry: if (fatal_signal_pending(current)) break; - *locked = 1; ret = down_read_killable(&mm->mmap_sem); if (ret) { BUG_ON(ret > 0); @@ -1108,6 +1107,7 @@ retry: break; } + *locked = 1; ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED, pages, NULL, locked); if (!*locked) {