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From: "zhengbin (A)" <zhengbin13@huawei.com>
To: Al Viro <viro@ZenIV.linux.org.uk>,
	Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	David Miller <davem@davemloft.net>,
	Jason Baron <jbaron@akamai.com>, <kgraul@linux.ibm.com>,
	<ktkhai@virtuozzo.com>, <kyeongdon.kim@lge.com>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	Netdev <netdev@vger.kernel.org>, <pabeni@redhat.com>,
	<syzkaller-bugs@googlegroups.com>, <xiyou.wangcong@gmail.com>,
	Christoph Hellwig <hch@lst.de>, <bcrl@kvack.org>,
	<linux-fsdevel@vger.kernel.org>, <linux-aio@kvack.org>,
	<houtao1@huawei.com>, <yi.zhang@huawei.com>
Subject: Re: [PATCH 3/8] aio_poll(): sanitize the logics after vfs_poll(), get rid of leak on error
Date: Thu, 7 Mar 2019 10:11:02 +0800	[thread overview]
Message-ID: <0c631d6f-48b6-3691-eec5-29eb55817346@huawei.com> (raw)
In-Reply-To: <20190307000316.31133-3-viro@ZenIV.linux.org.uk>

+	if (async && !apt.error)  --->may be this should be if (!async && !apt.error) ?

On 2019/3/7 8:03, Al Viro wrote:
> From: Al Viro <viro@zeniv.linux.org.uk>
> 
> We want iocb_put() happening on errors, to balance the extra reference
> we'd taken.  As it is, we end up with a leak.  The rules should be
> 	* error: iocb_put() to deal with the extra ref, return error,
> let the caller do another iocb_put().
> 	* async: iocb_put() to deal with the extra ref, return 0.
> 	* no error, event present immediately: aio_poll_complete() to
> report it, iocb_put() to deal with the extra ref, return 0.
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  fs/aio.c | 25 +++++++++++--------------
>  1 file changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/aio.c b/fs/aio.c
> index 3a8b894378e0..22b288997441 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1724,6 +1724,7 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
>  	struct kioctx *ctx = aiocb->ki_ctx;
>  	struct poll_iocb *req = &aiocb->poll;
>  	struct aio_poll_table apt;
> +	bool async = false;
>  	__poll_t mask;
>  
>  	/* reject any unknown events outside the normal event mask. */
> @@ -1760,30 +1761,26 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
>  
>  	spin_lock_irq(&ctx->ctx_lock);
>  	spin_lock(&req->head->lock);
> -	if (req->woken) {
> -		/* wake_up context handles the rest */
> -		mask = 0;
> +	if (req->woken) { /* already taken up by aio_poll_wake() */
> +		async = true;
>  		apt.error = 0;
> -	} else if (mask || apt.error) {
> -		/* if we get an error or a mask we are done */
> -		WARN_ON_ONCE(list_empty(&req->wait.entry));
> -		list_del_init(&req->wait.entry);
> -	} else {
> -		/* actually waiting for an event */
> +	} else if (!mask && !apt.error) { /* actually waiting for an event */
>  		list_add_tail(&aiocb->ki_list, &ctx->active_reqs);
>  		aiocb->ki_cancel = aio_poll_cancel;
> +		async = true;
> +	} else { /* if we get an error or a mask we are done */
> +		WARN_ON_ONCE(list_empty(&req->wait.entry));
> +		list_del_init(&req->wait.entry);
> +		/* no wakeup in the future either; aiocb is ours to dispose of */
>  	}
>  	spin_unlock(&req->head->lock);
>  	spin_unlock_irq(&ctx->ctx_lock);
>  
>  out:
> -	if (unlikely(apt.error))
> -		return apt.error;
> -
> -	if (mask)
> +	if (async && !apt.error)
>  		aio_poll_complete(aiocb, mask);
>  	iocb_put(aiocb);
> -	return 0;
> +	return apt.error;
>  }
>  
>  static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
> 


  reply	other threads:[~2019-03-07  2:11 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-03 10:22 KASAN: use-after-free Read in unix_dgram_poll syzbot
2019-03-03 13:55 ` Al Viro
2019-03-03 15:18   ` [PATCH] aio: prevent the final fput() in the middle of vfs_poll() (Re: KASAN: use-after-free Read in unix_dgram_poll) Al Viro
2019-03-03 18:37     ` Eric Dumazet
2019-03-03 19:44     ` Linus Torvalds
2019-03-03 20:13       ` Linus Torvalds
2019-03-03 20:30       ` Al Viro
2019-03-03 22:23         ` Linus Torvalds
2019-03-04  2:36           ` Al Viro
2019-03-04 21:22             ` Linus Torvalds
2019-03-07  0:03               ` [PATCH 1/8] aio: make sure file is pinned Al Viro
2019-03-07  0:03                 ` [PATCH 2/8] aio_poll_wake(): don't set ->woken if we ignore the wakeup Al Viro
2019-03-07  2:18                   ` Al Viro
2019-03-08 11:16                     ` zhengbin (A)
2019-03-07  0:03                 ` [PATCH 3/8] aio_poll(): sanitize the logics after vfs_poll(), get rid of leak on error Al Viro
2019-03-07  2:11                   ` zhengbin (A) [this message]
2019-03-07  0:03                 ` [PATCH 4/8] aio_poll(): get rid of weird refcounting Al Viro
2019-03-07  0:03                 ` [PATCH 5/8] make aio_read()/aio_write() return int Al Viro
2019-03-07  0:03                 ` [PATCH 6/8] move dropping ->ki_eventfd into iocb_put() Al Viro
2019-03-07  0:03                 ` [PATCH 7/8] deal with get_reqs_available() in aio_get_req() itself Al Viro
2019-03-07  0:03                 ` [PATCH 8/8] aio: move sanity checks and request allocation to io_submit_one() Al Viro
2019-03-07  0:23                 ` [PATCH 1/8] aio: make sure file is pinned Linus Torvalds
2019-03-07  0:41                   ` Al Viro
2019-03-07  0:48                     ` Al Viro
2019-03-07  1:20                       ` Al Viro
2019-03-07  1:30                         ` Linus Torvalds
2019-03-08  3:36                           ` Al Viro
2019-03-08 15:50                             ` Christoph Hellwig
2019-03-10  7:06                             ` Al Viro
2019-03-10  7:08                               ` [PATCH 1/8] pin iocb through aio Al Viro
2019-03-10  7:08                                 ` [PATCH 2/8] keep io_event in aio_kiocb Al Viro
2019-03-11 19:43                                   ` Christoph Hellwig
2019-03-11 21:17                                     ` Al Viro
2019-03-10  7:08                                 ` [PATCH 3/8] aio: store event at final iocb_put() Al Viro
2019-03-11 19:44                                   ` Christoph Hellwig
2019-03-11 21:13                                     ` Al Viro
2019-03-11 22:52                                       ` Al Viro
2019-03-10  7:08                                 ` [PATCH 4/8] Fix aio_poll() races Al Viro
2019-03-11 19:58                                   ` Christoph Hellwig
2019-03-11 21:06                                     ` Al Viro
2019-03-12 19:18                                       ` Christoph Hellwig
2019-03-10  7:08                                 ` [PATCH 5/8] make aio_read()/aio_write() return int Al Viro
2019-03-11 19:44                                   ` Christoph Hellwig
2019-03-10  7:08                                 ` [PATCH 6/8] move dropping ->ki_eventfd into iocb_destroy() Al Viro
2019-03-11 19:46                                   ` Christoph Hellwig
2019-03-10  7:08                                 ` [PATCH 7/8] deal with get_reqs_available() in aio_get_req() itself Al Viro
2019-03-11 19:46                                   ` Christoph Hellwig
2019-03-10  7:08                                 ` [PATCH 8/8] aio: move sanity checks and request allocation to io_submit_one() Al Viro
2019-03-11 19:48                                   ` Christoph Hellwig
2019-03-11 21:12                                     ` Al Viro
2019-03-11 19:41                                 ` [PATCH 1/8] pin iocb through aio Christoph Hellwig
2019-03-11 19:41                               ` [PATCH 1/8] aio: make sure file is pinned Christoph Hellwig
2019-03-04  7:53     ` [PATCH] aio: prevent the final fput() in the middle of vfs_poll() (Re: KASAN: use-after-free Read in unix_dgram_poll) Dmitry Vyukov

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