[PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal signal

From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	peterx@redhat.com, Hillf Danton <hdanton@sina.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	syzbot+3be1a33f04dc782e9fd5@syzkaller.appspotmail.com,
	Michal Hocko <mhocko@suse.com>
Subject: [PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal signal
Date: Wed,  8 Apr 2020 11:59:24 -0400	[thread overview]
Message-ID: <20200408155924.107722-1-peterx@redhat.com> (raw)

From: Hillf Danton <hdanton@sina.com>

__get_user_pages_locked() will return 0 instead of -EINTR after commit
4426e945df588 which added extra code to allow gup detect fatal signal
faster.  Restore that behavior.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times")
Reported-by: syzbot+3be1a33f04dc782e9fd5@syzkaller.appspotmail.com
Signed-off-by: Hillf Danton <hdanton@sina.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---

PS. Patch verified with syzbot.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 mm/gup.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index afce0bc47e70..6076df8e04a4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1326,8 +1326,11 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
 		 * start trying again otherwise it can loop forever.
 		 */
 
-		if (fatal_signal_pending(current))
+		if (fatal_signal_pending(current)) {
+			if (!pages_done)
+				pages_done = -EINTR;
 			break;
+		}
 
 		ret = down_read_killable(&mm->mmap_sem);
 		if (ret) {
-- 
2.24.1

