can: isotp: prevent race between isotp_bind() and isotp_setsockopt()

commit 2b17c400aeb44daf041627722581ade527bb3c1d upstream.

A race condition was found in isotp_setsockopt() which allows to
change socket options after the socket was bound.
For the specific case of SF_BROADCAST support, this might lead to possible
use-after-free because can_rx_unregister() is not called.

Checking for the flag under the socket lock in isotp_bind() and taking
the lock in isotp_setsockopt() fixes the issue.

Fixes: 921ca574cd38 ("can: isotp: add SF_BROADCAST support for functional addressing")
Link: https://lore.kernel.org/r/trinity-e6ae9efa-9afb-4326-84c0-f3609b9b8168-1620773528307@3c-app-gmx-bs06
Reported-by: Norbert Slusarek <nslusarek@gmx.net>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Norbert Slusarek <nslusarek@gmx.net>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/can/isotp.c b/net/can/isotp.c
index 37db4d232313da3cbb53fd7c9ddf0a76782cf74e..3f11d2b314b680851bf9ffdb5d93b8dee7d98081 100644 (file)
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1193,16 +1193,13 @@ static int isotp_getname(struct socket *sock, struct sockaddr *uaddr, int peer)
        return ISOTP_MIN_NAMELEN;
 }
 
-static int isotp_setsockopt(struct socket *sock, int level, int optname,
+static int isotp_setsockopt_locked(struct socket *sock, int level, int optname,
                            sockptr_t optval, unsigned int optlen)
 {
        struct sock *sk = sock->sk;
        struct isotp_sock *so = isotp_sk(sk);
        int ret = 0;
 
-       if (level != SOL_CAN_ISOTP)
-               return -EINVAL;
-
        if (so->bound)
                return -EISCONN;
 
@@ -1277,6 +1274,22 @@ static int isotp_setsockopt(struct socket *sock, int level, int optname,
        return ret;
 }
 
+static int isotp_setsockopt(struct socket *sock, int level, int optname,
+                           sockptr_t optval, unsigned int optlen)
+
+{
+       struct sock *sk = sock->sk;
+       int ret;
+
+       if (level != SOL_CAN_ISOTP)
+               return -EINVAL;
+
+       lock_sock(sk);
+       ret = isotp_setsockopt_locked(sock, level, optname, optval, optlen);
+       release_sock(sk);
+       return ret;
+}
+
 static int isotp_getsockopt(struct socket *sock, int level, int optname,
                            char __user *optval, int __user *optlen)
 {