netdev - [PATCH] net/9p: fix format string in p9_mount_tag

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Date:	Mon, 26 Jan 2015 19:48:16 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	linux-kernel@...r.kernel.org
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Eric Van Hensbergen <ericvh@...il.com>,
	Ron Minnich <rminnich@...dia.gov>,
	Latchesar Ionkov <lucho@...kov.net>,
	"David S. Miller" <davem@...emloft.net>,
	v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org,
	Andrey Ryabinin <a.ryabinin@...sung.com>
Subject: [PATCH] net/9p: fix format string in p9_mount_tag_show()

Using "%s" for non-NULL terminated string is quite
dangerous, since this causes reading out of bounds.
chan->tag is non-NULL terminated, so precision
must be specified for printing it.

Fixes: 86c8437383ac ("net/9p: Add sysfs mount_tag file for virtio 9P device")
Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
---
 net/9p/trans_virtio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index daa749c..f0d5f90 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -504,7 +504,8 @@ static ssize_t p9_mount_tag_show(struct device *dev,
 	vdev = dev_to_virtio(dev);
 	chan = vdev->priv;
 
-	return snprintf(buf, chan->tag_len + 1, "%s", chan->tag);
+	return snprintf(buf, chan->tag_len + 1, "%.*s",
+			chan->tag_len, chan->tag);
 }
 
 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
-- 
2.2.2

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