[PATCH 5.10 006/121] can: isotp: prevent race between isotp_bind() and isotp_setsockopt()

Greg Kroah-Hartman
2022-02-21T09:16:19Z

From: Norbert Slusarek <nslusarek@gmx.net>

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>
---
net/can/isotp.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)

--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1193,16 +1193,13 @@ static int isotp_getname(struct socket *
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 socke
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)
{