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From: Hillf Danton <hdanton@sina.com>
To: syzbot <syzbot+045b454ab35fd82a35fb@syzkaller.appspotmail.com>
Cc: linux-kernel@vger.kernel.org,
	syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [fs?] [io-uring?] general protection fault in __ep_remove
Date: Sat,  4 May 2024 11:23:45 +0800
Message-Id: <20240504032345.1992-1-hdanton@sina.com>
In-Reply-To: <0000000000002d631f0615918f1e@google.com>
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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;
 }
--