can: raw: fix ro->uniq use-after-free in raw_rcv()

raw_release() unregisters raw CAN receive filters via can_rx_unregister(),
but receiver deletion is deferred with call_rcu(). This leaves a window
where raw_rcv() may still be running in an RCU read-side critical section
after raw_release() frees ro->uniq, leading to a use-after-free of the
percpu uniq storage.

Move free_percpu(ro->uniq) out of raw_release() and into a raw-specific
socket destructor. can_rx_unregister() takes an extra reference to the
socket and only drops it from the RCU callback, so freeing uniq from
sk_destruct ensures the percpu area is not released until the relevant
callbacks have drained.

Fixes: 514ac99c64b2 ("can: fix multiple delivery of a single CAN frame for overlapping CAN filters")
Cc: stable@vger.kernel.org # v4.1+
Assisted-by: Bynario AI
Signed-off-by: Samuel Page <sam@bynar.io>
Link: https://patch.msgid.link/26ec626d-cae7-4418-9782-7198864d070c@bynar.io
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
[mkl: applied manually]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/net/can/raw.c b/net/can/raw.c
index eee244ffc31ecc0e1cc1aae29cd1d13a4e6b54ca..58a96e933debb5382e02fccf275cf95dde34edd8 100644 (file)
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -361,6 +361,14 @@ static int raw_notifier(struct notifier_block *nb, unsigned long msg,
        return NOTIFY_DONE;
 }
 
+static void raw_sock_destruct(struct sock *sk)
+{
+       struct raw_sock *ro = raw_sk(sk);
+
+       free_percpu(ro->uniq);
+       can_sock_destruct(sk);
+}
+
 static int raw_init(struct sock *sk)
 {
        struct raw_sock *ro = raw_sk(sk);
@@ -387,6 +395,8 @@ static int raw_init(struct sock *sk)
        if (unlikely(!ro->uniq))
                return -ENOMEM;
 
+       sk->sk_destruct = raw_sock_destruct;
+
        /* set notifier */
        spin_lock(&raw_notifier_lock);
        list_add_tail(&ro->notifier, &raw_notifier_list);
@@ -436,7 +446,6 @@ static int raw_release(struct socket *sock)
        ro->bound = 0;
        ro->dev = NULL;
        ro->count = 0;
-       free_percpu(ro->uniq);
 
        sock_orphan(sk);
        sock->sk = NULL;