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a=ed25519-sha256; c=relaxed/relaxed; t=1783413172; s=strato-dkim-0003; d=hartkopp.net; h=Message-ID:Date:Subject:Cc:To:From:Cc:Date:From:Subject:Sender; bh=1Y462xLZBMkfRXHyQMCplbxVmwrDTOCYDqlRLB3eTh0=; b=v3HSpbmO3+xzQZfdB8QwTxLArT4/XVJLyFflYAFarfOemHpSpjBTCpDLEuS0oFl9FK yaOJAJQAhC+q/3QEohCw== X-RZG-AUTH: ":P2MHfkW8eP4Mre39l357AZT/I7AY/7nT2yrDxb8mjH4JKvMdQv2tRkI16oOSW1Ti/f4PoH8=" Received: from vivo.lan by smtp.strato.de (RZmta 55.5.6 DYNA|AUTH) with ESMTPSA id Ka9fdb2678WqQPM (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits)) (Client did not present a certificate); Tue, 7 Jul 2026 10:32:52 +0200 (CEST) From: Oliver Hartkopp To: linux-can@vger.kernel.org Cc: Oliver Hartkopp , Nico Yip Subject: [PATCH] can: isotp: add missing synchronize_rcu() in isotp_notify() Date: Tue, 7 Jul 2026 10:32:28 +0200 Message-ID: <20260707083228.47629-1-socketcan@hartkopp.net> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-can@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="us-ascii" isotp_notify() unregisters the (RCU) CAN filters via can_rx_unregister() and clears so->bound without waiting for a grace period. isotp_release() uses so->bound to decide whether it needs to call synchronize_rcu() before cancelling so->rxtimer, so when NETDEV_UNREGISTER runs first it skips that synchronize_rcu() and can cancel the timer while an in-flight isotp_rcv() is still executing and about to re-arm it via isotp_send_fc(), leading to a use-after-free timer callback on the freed socket. Fixes: 14a4696bc311 ("can: isotp: isotp_release(): omit unintended hrtimer restart on socket release") Reported-by: Nico Yip (ZDI-CAN-31764) Signed-off-by: Oliver Hartkopp --- net/can/isotp.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/can/isotp.c b/net/can/isotp.c index c48b4a818297..008cee547213 100644 --- a/net/can/isotp.c +++ b/net/can/isotp.c @@ -1573,10 +1573,17 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg, isotp_rcv, sk); can_rx_unregister(dev_net(dev), dev, so->txid, SINGLE_MASK(so->txid), isotp_rcv_echo, sk); + + /* wait for in-flight isotp_rcv() callers to finish + * before clearing so->bound, so that isotp_release() + * cannot observe so->bound == 0 and skip its own + * synchronize_rcu() while a callback is still running + */ + synchronize_rcu(); } so->ifindex = 0; so->bound = 0; release_sock(sk); -- 2.53.0