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From: Kamal Mostafa <kamal@canonical.com>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        kernel-team@lists.ubuntu.com
Cc: Shuah Khan <shuahkh@osg.samsung.com>,
        Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
        Kamal Mostafa <kamal@canonical.com>
Subject: [PATCH 4.2.y-ckt 24/70] [media] au0828: fix au0828_v4l2_close() dev_state race condition
Date: Tue, 12 Apr 2016 13:52:09 -0700
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4.2.8-ckt8 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Shuah Khan <shuahkh@osg.samsung.com>

commit ed940cd27416f9887864b95e1f8f8845aa9d6391 upstream.

au0828_v4l2_close() check for dev_state == DEV_DISCONNECTED will fail to
detect the device disconnected state correctly, if au0828_v4l2_open() runs
to set the DEV_INITIALIZED bit. A loop test of bind/unbind found this bug
by increasing the likelihood of au0828_v4l2_open() occurring while unbind
is in progress. When au0828_v4l2_close() fails to detect that the device
is in disconnect state, it attempts to power down the device and fails with
the following general protection fault:

[  260.992962] Call Trace:
[  260.993008]  [<ffffffffa0f80f0f>] ? xc5000_sleep+0x8f/0xd0 [xc5000]
[  260.993095]  [<ffffffffa0f6803c>] ? fe_standby+0x3c/0x50 [tuner]
[  260.993186]  [<ffffffffa0ef541c>] au0828_v4l2_close+0x53c/0x620 [au0828]
[  260.993298]  [<ffffffffa0d08ec0>] v4l2_release+0xf0/0x210 [videodev]
[  260.993382]  [<ffffffff81570f9c>] __fput+0x1fc/0x6c0
[  260.993449]  [<ffffffff815714ce>] ____fput+0xe/0x10
[  260.993519]  [<ffffffff8116eb83>] task_work_run+0x133/0x1f0
[  260.993602]  [<ffffffff810035d0>] exit_to_usermode_loop+0x140/0x170
[  260.993681]  [<ffffffff810061ca>] syscall_return_slowpath+0x16a/0x1a0
[  260.993754]  [<ffffffff82835fb3>] entry_SYSCALL_64_fastpath+0xa6/0xa8

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/media/usb/au0828/au0828-video.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/au0828/au0828-video.c b/drivers/media/usb/au0828/au0828-video.c
index 1a362a0..5cc2bb1 100644
--- a/drivers/media/usb/au0828/au0828-video.c
+++ b/drivers/media/usb/au0828/au0828-video.c
@@ -1001,7 +1001,7 @@ static int au0828_v4l2_close(struct file *filp)
 		del_timer_sync(&dev->vbi_timeout);
 	}
 
-	if (dev->dev_state == DEV_DISCONNECTED)
+	if (dev->dev_state & DEV_DISCONNECTED)
 		goto end;
 
 	if (dev->users == 1) {
-- 
2.7.4