Re: [syzbot] [fs?] [io-uring?] general protection fault in __ep_remove

[Hillf Danton <hdanton@sina.com>]

On Mon, 08 Apr 2024 01:26:16 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    480e035fc4c7 Merge tag 'drm-next-2024-03-13' of https://gi..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10801175180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  480e035fc4c7

--- x/fs/eventpoll.c
+++ y/fs/eventpoll.c
@@ -991,9 +991,13 @@ static __poll_t ep_item_poll(const struc
 	__poll_t res;
 
 	pt->_key = epi->event.events;
-	if (!is_file_epoll(file))
-		res = vfs_poll(file, pt);
-	else
+	if (!is_file_epoll(file)) {
+		res = 0;
+		if (atomic_long_inc_not_zero(&file->f_count)) {
+			res = vfs_poll(file, pt);
+			fput(file);
+		}
+	} else
 		res = __ep_eventpoll_poll(file, pt, depth);
 	return res & epi->event.events;
 }
--