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From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	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>,
	zhengbin <zhengbin13@huawei.com>,
	bcrl@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-aio@kvack.org, houtao1@huawei.com, yi.zhang@huawei.com
Subject: Re: [PATCH 4/8] Fix aio_poll() races
Date: Mon, 11 Mar 2019 20:58:31 +0100	[thread overview]
Message-ID: <20190311195831.GA12807@lst.de> (raw)
In-Reply-To: <20190310070822.11564-4-viro@ZenIV.linux.org.uk>

Where do we put the second iocb reference in case we return from
vfs_poll without ever being woken?

Also it seems like the complete code would still benefit from a little
helper, something like:

diff --git a/fs/aio.c b/fs/aio.c
index b2a5c7b3a1fe..8415e5e484ce 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1611,6 +1611,13 @@ static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb,
 	return 0;
 }
 
+static void aio_poll_finish(struct aio_kiocb *iocb, __poll_t mask)
+{
+	list_del_init(&iocb->ki_list);
+	iocb->ki_res.res = mangle_poll(mask);
+	iocb->poll.done = true;
+}
+
 static void aio_poll_complete_work(struct work_struct *work)
 {
 	struct poll_iocb *req = container_of(work, struct poll_iocb, work);
@@ -1635,9 +1642,7 @@ static void aio_poll_complete_work(struct work_struct *work)
 		spin_unlock_irq(&ctx->ctx_lock);
 		return;
 	}
-	list_del_init(&iocb->ki_list);
-	iocb->ki_res.res = mangle_poll(mask);
-	req->done = true;
+	aio_poll_finish(iocb, mask);
 	spin_unlock_irq(&ctx->ctx_lock);
 
 	iocb_put(iocb);
@@ -1674,24 +1679,20 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
 
 	list_del_init(&req->wait.entry);
 
-	if (mask) {
+	if (mask && spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) {
 		/*
 		 * Try to complete the iocb inline if we can. Use
 		 * irqsave/irqrestore because not all filesystems (e.g. fuse)
 		 * call this function with IRQs disabled and because IRQs
 		 * have to be disabled before ctx_lock is obtained.
 		 */
-		if (spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) {
-			list_del(&iocb->ki_list);
-			iocb->ki_res.res = mangle_poll(mask);
-			req->done = true;
-			spin_unlock_irqrestore(&iocb->ki_ctx->ctx_lock, flags);
-			iocb_put(iocb);
-			return 1;
-		}
+		aio_poll_finish(iocb, mask);
+		spin_unlock_irqrestore(&iocb->ki_ctx->ctx_lock, flags);
+		iocb_put(iocb);
+	} else {
+		schedule_work(&req->work);
 	}
 
-	schedule_work(&req->work);
 	return 1;
 }
 

  reply	other threads:[~2019-03-11 19:58 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)
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 [this message]
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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