From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@lst.de>
Cc: Avi Kivity <avi@scylladb.com>,
linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
netdev@vger.kernel.org, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 08/31] aio: implement IOCB_CMD_POLL
Date: Wed, 23 May 2018 01:49:04 +0100 [thread overview]
Message-ID: <20180523004904.GH30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180523004530.GG30522@ZenIV.linux.org.uk>
On Wed, May 23, 2018 at 01:45:30AM +0100, Al Viro wrote:
> Oh, bugger...
>
> wakeup
> removed from queue
> schedule __aio_poll_complete()
>
> cancel
> grab ctx->lock
> remove from list
> work
> aio_complete()
> check if it's in the list
> it isn't, move on to free the sucker
> cancel
> call ->ki_cancel()
> BOOM
>
> Looks like we want to call ->ki_cancel() *BEFORE* removing from the list,
> as well as doing fput() after aio_complete(). The same ordering, BTW, goes
> for aio_read() et.al.
>
> Look:
> CPU1: io_cancel() grabs ->ctx_lock, finds iocb and removes it from the list.
> CPU2: aio_rw_complete() on that iocb. Since the sucker is not in the list
> anymore, we do NOT spin on ->ctx_lock and proceed to free iocb
> CPU1: pass freed iocb to ->ki_cancel(). BOOM.
BTW, it seems that the mainline is vulnerable to this one. I might be
missing something, but...
next prev parent reply other threads:[~2018-05-23 0:49 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-22 11:30 aio poll and a new in-kernel poll API V12 Christoph Hellwig
2018-05-22 11:30 ` [PATCH 01/31] fs: unexport poll_schedule_timeout Christoph Hellwig
2018-05-22 11:30 ` [PATCH 02/31] fs: cleanup do_pollfd Christoph Hellwig
2018-05-22 11:30 ` [PATCH 03/31] fs: update documentation to mention __poll_t and match the code Christoph Hellwig
2018-05-22 11:30 ` [PATCH 04/31] fs: add new vfs_poll and file_can_poll helpers Christoph Hellwig
2018-05-22 11:30 ` [PATCH 05/31] fs: introduce new ->get_poll_head and ->poll_mask methods Christoph Hellwig
2018-05-22 11:30 ` [PATCH 06/31] aio: simplify KIOCB_KEY handling Christoph Hellwig
2018-05-22 11:30 ` [PATCH 07/31] aio: simplify cancellation Christoph Hellwig
2018-05-22 11:30 ` [PATCH 08/31] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-05-22 22:05 ` Al Viro
2018-05-23 0:45 ` Al Viro
2018-05-23 0:49 ` Al Viro [this message]
2018-05-23 1:43 ` YAaioRace (was Re: [PATCH 08/31] aio: implement IOCB_CMD_POLL) Al Viro
2018-05-22 11:30 ` [PATCH 09/31] aio: try to complete poll iocbs without context switch Christoph Hellwig
2018-05-22 11:30 ` [PATCH 10/31] net: refactor socket_poll Christoph Hellwig
2018-05-22 11:30 ` [PATCH 11/31] net: add support for ->poll_mask in proto_ops Christoph Hellwig
2018-05-22 11:30 ` [PATCH 12/31] net: remove sock_no_poll Christoph Hellwig
2018-05-22 11:30 ` [PATCH 13/31] net/tcp: convert to ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 14/31] net/unix: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 15/31] net: convert datagram_poll users tp ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 16/31] net/dccp: convert to ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 17/31] net/atm: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 18/31] net/vmw_vsock: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 19/31] net/tipc: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 20/31] net/sctp: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 21/31] net/bluetooth: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 22/31] net/caif: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 23/31] net/nfc: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 24/31] net/phonet: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 25/31] net/iucv: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 26/31] net/rxrpc: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 27/31] crypto: af_alg: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 28/31] pipe: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 29/31] eventfd: switch " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 30/31] timerfd: convert " Christoph Hellwig
2018-05-22 16:59 ` Sergei Shtylyov
2018-05-22 11:31 ` [PATCH 31/31] random: " Christoph Hellwig
2018-05-22 22:07 ` aio poll and a new in-kernel poll API V12 Al Viro
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