linux-kernel - [PATCH 5.2 213/215] io_uring: ensure ->list is initialized for poll commands

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Message-Id: <20190729190816.805465347@linuxfoundation.org>
Date:   Mon, 29 Jul 2019 21:23:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Daniel Kozak <kozzi11@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.2 213/215] io_uring: ensure ->list is initialized for poll commands

From: Jens Axboe <axboe@...nel.dk>

commit 36703247d5f52a679df9da51192b6950fe81689f upstream.

Daniel reports that when testing an http server that uses io_uring
to poll for incoming connections, sometimes it hard crashes. This is
due to an uninitialized list member for the io_uring request. Normally
this doesn't trigger and none of the test cases caught it.

Reported-by: Daniel Kozak <kozzi11@...il.com>
Tested-by: Daniel Kozak <kozzi11@...il.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/io_uring.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1489,6 +1489,8 @@ static int io_poll_add(struct io_kiocb *
 	INIT_LIST_HEAD(&poll->wait.entry);
 	init_waitqueue_func_entry(&poll->wait, io_poll_wake);
 
+	INIT_LIST_HEAD(&req->list);
+
 	mask = vfs_poll(poll->file, &ipt.pt) & poll->events;
 
 	spin_lock_irq(&ctx->completion_lock);