[PATCH] net/9p: use memcpy() instead of snprintf() in p9_mount_tag_show()

[Andrey Ryabinin]

p9_mount_tag_show() uses '%s' format string to print
non-NULL terminated chan->tag string. This leads
to out of bounds memory read, because format '%s'
implies that string is NULL-terminated.

The length of string is know here, so its simpler and safer
to use memcpy instead of snprintf().

Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
---
 net/9p/trans_virtio.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index daa749c..9d64145 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -504,7 +504,10 @@ 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);
+	memcpy(buf, chan->tag, chan->tag_len);
+	buf[chan->tag_len] = 0;
+
+	return chan->tag_len + 1;
 }
 
 static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
-- 
2.2.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/