linux-kernel - [PATCH v2] [SCSI] mpt2sas: fix double mutex lock in NON

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Message-Id: <1346164683-9315-1-git-send-email-khoroshilov@ispras.ru>
Date:	Tue, 28 Aug 2012 18:38:02 +0400
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	"James E.J. Bottomley" <JBottomley@...allels.com>
Cc:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	linux-scsi@...r.kernel.org,
	Nagalakshmi Nandigama <nagalakshmi.nandigama@....com>,
	Sreekanth.Reddy@....com, linux-kernel@...r.kernel.org,
	ldv-project@...ras.ru
Subject: [PATCH v2] [SCSI] mpt2sas: fix double mutex lock in NON_BLOCKING state

If state is NON_BLOCKING and mutex_trylock is succeed,
the control flow goes to mutex_lock_interruptible() that is a deadlock.

The previous version of the patch becomes obsolete after 
code movement in commit 913809f6.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
---
 drivers/scsi/mpt2sas/mpt2sas_ctl.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/mpt2sas/mpt2sas_ctl.c b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
index 49bdd2d..d29ea56 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_ctl.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
@@ -2181,8 +2181,10 @@ _ctl_ioctl_main(struct file *file, unsigned int cmd, void __user *arg,
 		return -EAGAIN;
 
 	state = (file->f_flags & O_NONBLOCK) ? NON_BLOCKING : BLOCKING;
-	if (state == NON_BLOCKING && !mutex_trylock(&ioc->ctl_cmds.mutex))
-		return -EAGAIN;
+	if (state == NON_BLOCKING) {
+		if (!mutex_trylock(&ioc->ctl_cmds.mutex))
+			return -EAGAIN;
+	}
 	else if (mutex_lock_interruptible(&ioc->ctl_cmds.mutex))
 		return -ERESTARTSYS;
 
-- 
1.7.9.5

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