[PATCH] [SCSI] mpt2sas: fix double mutex lock in NON_BLOCKING state

[Alexey Khoroshilov]

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

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

Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
---
 drivers/scsi/mpt2sas/mpt2sas_ctl.c |   24 ++++++++++++++++--------
 1 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/mpt2sas/mpt2sas_ctl.c b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
index 1c6d2b4..9bd7ffc 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_ctl.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
@@ -648,8 +648,10 @@ _ctl_do_mpt_command(struct MPT2SAS_ADAPTER *ioc,
 
 	issue_reset = 0;
 
-	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;
 
@@ -1587,8 +1589,10 @@ _ctl_diag_register(void __user *arg, enum block_state state)
 	if (_ctl_verify_adapter(karg.hdr.ioc_number, &ioc) == -1 || !ioc)
 		return -ENODEV;
 
-	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;
 	rc = _ctl_diag_register_2(ioc, &karg);
@@ -1932,8 +1936,10 @@ _ctl_diag_release(void __user *arg, enum block_state state)
 		return 0;
 	}
 
-	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;
 
@@ -2033,8 +2039,10 @@ _ctl_diag_read_buffer(void __user *arg, enum block_state state)
 	}
 	/* Get a free request frame and save the message context.
 	*/
-	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;
 
-- 
1.7.1

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