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a=ed25519-sha256; c=relaxed/relaxed; t=1784889255; s=strato-dkim-0003; d=hartkopp.net; h=References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Cc:Date: From:Subject:Sender; bh=5ERx3PJQ3f7TyBRDNsOywdWQR3zqTTDkSccBfQekVDM=; b=bvQ/9IS0S0zQoSJPPhGpoiBWAm2l1F2DwgdgqKOujeXDULIARH2B+1TMzJU5NYO9Mr T4z2MSQcTTAA9RFGFpBg== X-RZG-AUTH: ":P2MHfkW8eP4Mre39l357AZT/I7AY/7nT2yrDxb8mjH4JKvMdQv2tRkI16oOSW1Ti/f4PoH8=" Received: from vivo.lan by smtp.strato.de (RZmta 55.5.6 SBL|AUTH) with ESMTPSA id K5281926OAYFtMK (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits)) (Client did not present a certificate); Fri, 24 Jul 2026 12:34:15 +0200 (CEST) From: Oliver Hartkopp To: stable@vger.kernel.org Cc: Oliver Hartkopp , Marc Kleine-Budde Subject: [PATCH 6.6.y 1/2] can: isotp: fix use-after-free race with concurrent NETDEV_UNREGISTER Date: Fri, 24 Jul 2026 12:34:08 +0200 Message-ID: <20260724103409.17867-1-socketcan@hartkopp.net> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026072053-spoils-overlying-285a@gregkh> References: <2026072053-spoils-overlying-285a@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="us-ascii" commit 20bab8b88baac140ca3701116e1d486c7f51e311 upstream. isotp_release() looked up the bound network device via dev_get_by_index() using the stored ifindex. During device unregistration the device is unlisted from the ifindex hash before the NETDEV_UNREGISTER notifier chain runs, so a concurrent isotp_release() could find no device, skip can_rx_unregister() entirely, and still proceed to free the socket. Since isotp_release() had already removed itself from the isotp notifier list at that point, isotp_notify() would never get a chance to clean up either, leaving a stale CAN filter that keeps pointing at the freed socket. Fix this the same way raw.c already does: hold a tracked reference to the bound net_device in the socket (so->dev/so->dev_tracker) from bind() onward instead of re-resolving it from the ifindex, and serialize bind()/release() with rtnl_lock() so that so->dev is always consistent with what the NETDEV_UNREGISTER notifier sees. so->dev stays valid regardless of ifindex-hash unlisting, and is only ever cleared by whichever of isotp_release()/isotp_notify() gets there first, so the filter is always removed exactly once. isotp_bind() now rejects a (re)bind with -EAGAIN while so->[tx|rx].state isn't ISOTP_IDLE yet, so a timer left running by a prior NETDEV_UNREGISTER can't act on a newly bound so->ifindex. Both checks share the same lock_sock() section, so there is no window in which a concurrent isotp_notify() clearing so->bound could be missed. Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol") Reported-by: sashiko-bot@kernel.org Closes: https://lore.kernel.org/linux-can/20260707101420.47F261F000E9@smtp.kernel.org/ Signed-off-by: Oliver Hartkopp Link: https://patch.msgid.link/20260712-isotp-fixes-v10-2-793a1b1ce17f@hartkopp.net Cc: stable@kernel.org Signed-off-by: Marc Kleine-Budde Signed-off-by: Oliver Hartkopp --- net/can/isotp.c | 88 ++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 59 insertions(+), 29 deletions(-) diff --git a/net/can/isotp.c b/net/can/isotp.c index 80adf73..b906fcd 100644 --- a/net/can/isotp.c +++ b/net/can/isotp.c @@ -150,6 +150,7 @@ struct isotp_sock { struct sock sk; int bound; int ifindex; + struct net_device *dev; canid_t txid; canid_t rxid; ktime_t tx_gap; @@ -962,6 +963,14 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size) goto err_event_drop; } + /* so->bound is only checked once above - a wakeup may have + * unbound/rebound the socket meanwhile, so re-validate it + */ + if (!so->bound) { + err = -EADDRNOTAVAIL; + goto err_out_drop; + } + /* PDU size > default => try max_pdu_size */ if (size > so->tx.buflen && so->tx.buflen < max_pdu_size) { u8 *newbuf = kmalloc(max_pdu_size, GFP_KERNEL); @@ -1197,28 +1206,30 @@ static int isotp_release(struct socket *sock) list_del(&so->notifier); spin_unlock(&isotp_notifier_lock); + rtnl_lock(); lock_sock(sk); - /* remove current filters & unregister */ - if (so->bound) { - if (so->ifindex) { - struct net_device *dev; - - dev = dev_get_by_index(net, so->ifindex); - if (dev) { - if (isotp_register_rxid(so)) - can_rx_unregister(net, dev, so->rxid, - SINGLE_MASK(so->rxid), - isotp_rcv, sk); - - can_rx_unregister(net, dev, so->txid, - SINGLE_MASK(so->txid), - isotp_rcv_echo, sk); - dev_put(dev); - } - } + /* remove current filters & unregister + * tracked reference so->dev is taken at bind() time with rtnl_lock + */ + if (so->bound && so->dev) { + if (isotp_register_rxid(so)) + can_rx_unregister(net, so->dev, so->rxid, + SINGLE_MASK(so->rxid), + isotp_rcv, sk); + + can_rx_unregister(net, so->dev, so->txid, + SINGLE_MASK(so->txid), + isotp_rcv_echo, sk); + dev_put(so->dev); } + so->ifindex = 0; + so->bound = 0; + so->dev = NULL; + + rtnl_unlock(); + /* Always wait for a grace period before touching the timers below. * A concurrent NETDEV_UNREGISTER may have already unregistered our * filters and cleared so->bound in isotp_notify() without waiting @@ -1231,9 +1242,6 @@ static int isotp_release(struct socket *sock) hrtimer_cancel(&so->txtimer); hrtimer_cancel(&so->rxtimer); - so->ifindex = 0; - so->bound = 0; - sock_orphan(sk); sock->sk = NULL; @@ -1287,6 +1295,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len) if (!addr->can_ifindex) return -ENODEV; + rtnl_lock(); lock_sock(sk); if (so->bound) { @@ -1294,6 +1303,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len) goto out; } + /* A transmission or reception that outlived a previous binding + * (unbound by NETDEV_UNREGISTER) may still be draining; the FC/echo + * and RX watchdog timers bound how long this takes. Checked together + * with so->bound in the same lock_sock() section above, so there is + * no window in which a concurrent isotp_notify() could be missed. + */ + if (so->tx.state != ISOTP_IDLE || so->rx.state != ISOTP_IDLE) { + err = -EAGAIN; + goto out; + } + /* ensure different CAN IDs when the rx_id is to be registered */ if (isotp_register_rxid(so) && rx_id == tx_id) { err = -EADDRNOTAVAIL; @@ -1306,14 +1326,12 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len) goto out; } if (dev->type != ARPHRD_CAN) { - dev_put(dev); err = -ENODEV; - goto out; + goto out_put_dev; } - if (dev->mtu < so->ll.mtu) { - dev_put(dev); + if (READ_ONCE(dev->mtu) < so->ll.mtu) { err = -EINVAL; - goto out; + goto out_put_dev; } if (!(dev->flags & IFF_UP)) notify_enetdown = 1; @@ -1331,16 +1349,25 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len) can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id), isotp_rcv_echo, sk, "isotpe", sk); - dev_put(dev); - /* switch to new settings */ so->ifindex = ifindex; so->rxid = rx_id; so->txid = tx_id; so->bound = 1; + /* bind() ok -> hold a reference for so->dev so that isotp_release() + * can safely reach the device later, even if a concurrent + * NETDEV_UNREGISTER has already unlisted it by ifindex. + */ + so->dev = dev; + dev_hold(so->dev); + +out_put_dev: + /* remove potential reference from dev_get_by_index() */ + dev_put(dev); out: release_sock(sk); + rtnl_unlock(); if (notify_enetdown) { sk->sk_err = ENETDOWN; @@ -1543,7 +1570,7 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg, if (!net_eq(dev_net(dev), sock_net(sk))) return; - if (so->ifindex != dev->ifindex) + if (so->dev != dev) return; switch (msg) { @@ -1559,10 +1586,12 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg, can_rx_unregister(dev_net(dev), dev, so->txid, SINGLE_MASK(so->txid), isotp_rcv_echo, sk); + dev_put(so->dev); } so->ifindex = 0; so->bound = 0; + so->dev = NULL; release_sock(sk); sk->sk_err = ENODEV; @@ -1622,6 +1651,7 @@ static int isotp_init(struct sock *sk) so->ifindex = 0; so->bound = 0; + so->dev = NULL; so->opt.flags = CAN_ISOTP_DEFAULT_FLAGS; so->opt.ext_address = CAN_ISOTP_DEFAULT_EXT_ADDRESS; -- 2.43.0