From: Mike Snitzer <snitzer@gmail.com>
Date: Wed, 2 Apr 2008 20:04:47 +0000 (-0700)
Subject: nbd: prevent sock_xmit from attempting to use a NULL socket
X-Git-Tag: v2.6.25-rc9~87
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=ffc41cf8dbb1b895a87daf47d0e5bf6dfbfcab4c;p=linux-2.6-omap-h63xx.git

nbd: prevent sock_xmit from attempting to use a NULL socket

NBD does not protect the nbd_device's socket from becoming NULL during
receives.

This closes a race with the NBD_CLEAR_SOCK ioctl (nbd-client -d) setting
the nbd_device's socket to NULL right before NBD calls sock_xmit.

Signed-off-by: Mike Snitzer <snitzer@gmail.com>
Cc: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index b53fdb0a282..60cc54368b6 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -153,6 +153,12 @@ static int sock_xmit(struct nbd_device *lo, int send, void *buf, int size,
 	struct kvec iov;
 	sigset_t blocked, oldset;
 
+	if (unlikely(!sock)) {
+		printk(KERN_ERR "%s: Attempted %s on closed socket in sock_xmit\n",
+		       lo->disk->disk_name, (send ? "send" : "recv"));
+		return -EINVAL;
+	}
+
 	/* Allow interception of SIGKILL only
 	 * Don't allow other signals to interrupt the transmission */
 	siginitsetinv(&blocked, sigmask(SIGKILL));