[Devel] [PATCH RHEL8 COMMIT] ms/vhost: Check docket sk_family instead of call getname

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-193.6.3.vz8.4.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-193.6.3.vz8.4.9
------>
commit 8357bcb2d0eb726d809a7757f260485046b9aadd
Author: Eugenio Pérez <eperezma at redhat.com>
Date:   Wed Sep 30 17:25:37 2020 +0300

    ms/vhost: Check docket sk_family instead of call getname
    
    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 at syzkaller.appspotmail.com
    Signed-off-by: Eugenio Pérez <eperezma at redhat.com>
    Acked-by: Michael S. Tsirkin <mst at redhat.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    
    Commit 42d84c8490f9f0931786f1623191fcab397c3d64 in the mainline kernel.
    
    CVE-2020-10942
    https://jira.sw.ru/browse/PSBM-120641
    
    Signed-off-by: Evgenii Shatokhin <eshatokhin at virtuozzo.com>
---
 drivers/vhost/net.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index f0ed73eac6d3..cd0831c488f8 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1415,10 +1415,6 @@ 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 r;
 	struct socket *sock = sockfd_lookup(fd, &r);
 
@@ -1431,11 +1427,7 @@ static struct socket *get_raw_socket(int fd)
 		goto err;
 	}
 
-	r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa, 0);
-	if (r < 0)
-		goto err;
-
-	if (uaddr.sa.sll_family != AF_PACKET) {
+	if (sock->sk->sk_family != AF_PACKET) {
 		r = -EPFNOSUPPORT;
 		goto err;
 	}