linux-kernel - [PATCH 2/8] firewire: cdev: fix race in iso context creation

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Message-ID: <tkrat.9e7edf6dc0ca32ad@s5r6.in-berlin.de>
Date:	Sun, 20 Jun 2010 22:51:05 +0200 (CEST)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 2/8] firewire: cdev: fix race in iso context creation

Date: Mon, 14 Jun 2010 11:46:25 +0200
From: Clemens Ladisch <clemens@...isch.de>

Protect the client's iso context pointer against a race that can happen
when more than one creation call is executed at the same time.

Signed-off-by: Clemens Ladisch <clemens@...isch.de>
Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
 drivers/firewire/core-cdev.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Index: b/drivers/firewire/core-cdev.c
===================================================================
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -865,10 +865,6 @@ static int ioctl_create_iso_context(stru
 	struct fw_cdev_create_iso_context *a = &arg->create_iso_context;
 	struct fw_iso_context *context;
 
-	/* We only support one context at this time. */
-	if (client->iso_context != NULL)
-		return -EBUSY;
-
 	if (a->channel > 63)
 		return -EINVAL;
 
@@ -893,10 +889,17 @@ static int ioctl_create_iso_context(stru
 	if (IS_ERR(context))
 		return PTR_ERR(context);
 
+	/* We only support one context at this time. */
+	spin_lock_irq(&client->lock);
+	if (client->iso_context != NULL) {
+		spin_unlock_irq(&client->lock);
+		fw_iso_context_destroy(context);
+		return -EBUSY;
+	}
 	client->iso_closure = a->closure;
 	client->iso_context = context;
+	spin_unlock_irq(&client->lock);
 
-	/* We only support one context at this time. */
 	a->handle = 0;
 
 	return 0;

-- 
Stefan Richter
-=====-==-=- -==- =-=--
http://arcgraph.de/sr/

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