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From: Manjunath Patil <manjunath.b.patil@oracle.com>
To: boris.ostrovsky@oracle.com, jgross@suse.com,
	konrad.wilk@oracle.com, roger.pau@citrix.com
Cc: axboe@kernel.dk, xen-devel@lists.xenproject.org,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: [PATCH v2] xen-blkfront: fix kernel panic with blkfront_remove()
Date: Thu,  8 Nov 2018 17:10:43 -0800	[thread overview]
Message-ID: <1541725843-2019-1-git-send-email-manjunath.b.patil@oracle.com> (raw)

When we try to detach the device, blkfront_remove() tries to access
blkfront_info leading to kernel panic.

Typical call stack involving panic -
 #10 page_fault at ffffffff816f25df
     [exception RIP: blkif_free+46]
 #11 blkfront_remove at ffffffffa004de47 [xen_blkfront]
 #12 xenbus_dev_remove at ffffffff813faa4c
 #13 __device_release_driver at ffffffff814769aa
 #14 device_release_driver at ffffffff81476a63
 #15 bus_remove_device at ffffffff814762eb
 #16 device_del at ffffffff81472684
 #17 device_unregister at ffffffff814727e2
 #18 xenbus_dev_changed at ffffffff813fa89f
 #19 frontend_changed at ffffffff813fca19
 #20 xenwatch_thread at ffffffff813f88f9
 #21 kthread at ffffffff810a486b
 #22 ret_from_fork at ffffffff816ed2a8

Cc: stable@vger.kernel.org
Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com>
---
v2: style change. added the missing space b/w if and (
---
 drivers/block/xen-blkfront.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index dc8fe25..2d8b10d 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -2496,6 +2496,9 @@ static int blkfront_remove(struct xenbus_device *xbdev)
 
 	dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename);
 
+	if (!info)
+		return 0;
+
 	blkif_free(info, 0);
 
 	mutex_lock(&info->mutex);
-- 
1.7.1


             reply	other threads:[~2018-11-09  1:09 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-09  1:10 Manjunath Patil [this message]
2018-11-09  6:16 ` Juergen Gross
2018-11-09 19:08   ` [Xen-devel] " Manjunath Patil

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