[cip-dev] [PATCH 4.4] vhost: Check docket sk_family instead of call getname

From: Pavel Machek <pavel@ucw.cz>
To: cip-dev@lists.cip-project.org, stable@kernel.org,
	eperezma@redhat.com, mst@redhat.com, davem@davemloft.net
Subject: [cip-dev] [PATCH 4.4] vhost: Check docket sk_family instead of call getname
Date: Fri, 27 Mar 2020 08:57:20 +0100	[thread overview]
Message-ID: <20200327075720.GA32000@duo.ucw.cz> (raw)


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From: Eugenio Pérez <eperezma@redhat.com>

Doing so, we save one call to get data we already have in the struct.

Also, since there is no guarantee that getname use sockaddr_ll
parameter beyond its size, we add a little bit of security here.
It should do not do beyond MAX_ADDR_LEN, but syzbot found that
ax25_getname writes more (72 bytes, the size of full_sockaddr_ax25,
versus 20 + 32 bytes of sockaddr_ll + MAX_ADDR_LEN in syzbot repro).

Fixes: 3a4d5c94e9593 ("vhost_net: a kernel-level virtio server")
Reported-by: syzbot+f2a62d07a5198c819c7b@syzkaller.appspotmail.com
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Upstream: 42d84c8490f9f0931786f1623191fcab397c3d64
Signed-off-by: Pavel Machek <pavel@denx.de>
---
 drivers/vhost/net.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

---

Since it is a security problem, I backported the patch to 4.4. I
compile tested it on cip test farm, but it was only built for single
target, probably due to too big config.

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 1459dc9fd701..5efac33c29dc 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -815,11 +815,7 @@ static int vhost_net_release(struct inode *inode, struct file *f)
 
 static struct socket *get_raw_socket(int fd)
 {
-	struct {
-		struct sockaddr_ll sa;
-		char  buf[MAX_ADDR_LEN];
-	} uaddr;
-	int uaddr_len = sizeof uaddr, r;
+	int r;
 	struct socket *sock = sockfd_lookup(fd, &r);
 
 	if (!sock)
@@ -831,12 +827,7 @@ static struct socket *get_raw_socket(int fd)
 		goto err;
 	}
 
-	r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa,
-			       &uaddr_len, 0);
-	if (r)
-		goto err;
-
-	if (uaddr.sa.sll_family != AF_PACKET) {
+	if (sock->sk->sk_family != AF_PACKET) {
 		r = -EPFNOSUPPORT;
 		goto err;
 	}
-- 
2.20.1


-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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