linux-kernel - [PATCH 3.16.y-ckt 066/144] target: Fix virtual LUN=0 target_configure

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Message-Id: <1429630329-21748-67-git-send-email-luis.henriques@canonical.com>
Date:	Tue, 21 Apr 2015 16:30:51 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Claudio Fleiner <cmf@...erainc.com>,
	Christoph Hellwig <hch@....de>,
	Nicholas Bellinger <nab@...ux-iscsi.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 066/144] target: Fix virtual LUN=0 target_configure_device failure OOPs

3.16.7-ckt10 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab@...ux-iscsi.org>

commit 5f7da044f8bc1cfb21c962edf34bd5699a76e7ae upstream.

This patch fixes a NULL pointer dereference triggered by a late
target_configure_device() -> alloc_workqueue() failure that results
in target_free_device() being called with DF_CONFIGURED already set,
which subsequently OOPses in destroy_workqueue() code.

Currently this only happens at modprobe target_core_mod time when
core_dev_setup_virtual_lun0() -> target_configure_device() fails,
and the explicit target_free_device() gets called.

To address this bug originally introduced by commit 0fd97ccf45, go
ahead and move DF_CONFIGURED to end of target_configure_device()
code to handle this special failure case.

Reported-by: Claudio Fleiner <cmf@...erainc.com>
Cc: Claudio Fleiner <cmf@...erainc.com>
Cc: Christoph Hellwig <hch@....de>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/target/target_core_device.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index e205bdbe14b2..5478aca8f4e6 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -1591,8 +1591,6 @@ int target_configure_device(struct se_device *dev)
 	ret = dev->transport->configure_device(dev);
 	if (ret)
 		goto out;
-	dev->dev_flags |= DF_CONFIGURED;
-
 	/*
 	 * XXX: there is not much point to have two different values here..
 	 */
@@ -1654,6 +1652,8 @@ int target_configure_device(struct se_device *dev)
 	list_add_tail(&dev->g_dev_node, &g_device_list);
 	mutex_unlock(&g_device_mutex);
 
+	dev->dev_flags |= DF_CONFIGURED;
+
 	return 0;
 
 out_free_alua:
--
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