linux-kernel - Re: [syzbot] [io-uring?] KASAN: slab-use-after-free Read in io_waitid

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Message-ID: <7c0346f9-e90c-4c15-a2d6-b2d40005361c@kernel.dk>
Date: Tue, 7 Oct 2025 07:20:08 -0600
From: Jens Axboe <axboe@...nel.dk>
To: syzbot <syzbot+b9e83021d9c642a33d8c@...kaller.appspotmail.com>,
 io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [io-uring?] KASAN: slab-use-after-free Read in
 io_waitid_wait

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git

diff --git a/io_uring/waitid.c b/io_uring/waitid.c
index 26c118f3918d..f25110fb1b12 100644
--- a/io_uring/waitid.c
+++ b/io_uring/waitid.c
@@ -230,13 +230,14 @@ static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
 	if (!pid_child_should_wake(wo, p))
 		return 0;
 
+	list_del_init(&wait->entry);
+
 	/* cancel is in progress */
 	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
 		return 1;
 
 	req->io_task_work.func = io_waitid_cb;
 	io_req_task_work_add(req);
-	list_del_init(&wait->entry);
 	return 1;
 }
 

-- 
Jens Axboe