From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32B1EEEC0 for ; Sun, 1 Mar 2026 19:45:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772394352; cv=none; b=E816rdv7p0UkG77eq3Alq34Dss4WtO8AE0J2zBQ+ERXg+XnDenl2QW99wcCGbEKFn+0RoHPBt8rQ7i6qgozY/gzC33suyWRGPwUqIGuIFDXarM4XZGcyKKyYmvhJIEtsqfO1kwW3E7RKzZD6vVrKJ++crnSbEfH4dyfd3wqf3Qo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772394352; c=relaxed/simple; bh=58XDJ2Xb3PSp3pzdLNs0B+8vC7iHFWVRHOpUoQlJOMY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=lI+VW/TAME0gUYhiMs0UszmhUUvKzKxrZPaQzgdsci0XlJ7revvFM11LCPztwhKiwTK/E3H6meb686ARzW3hoR5Bm9eljaqvBU0lGIp+t0taHj5BDLDhn4zTgCm1VRZVj+uYPet8M2AvIXR8BQPc7QoJtpJPy2fiU90wodVWbUc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Jiqfns1s; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Jiqfns1s" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6655AC116C6; Sun, 1 Mar 2026 19:45:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772394351; bh=58XDJ2Xb3PSp3pzdLNs0B+8vC7iHFWVRHOpUoQlJOMY=; h=From:To:Cc:Subject:Date:From; b=Jiqfns1sHZ0I8OKlw/cqU169NH5tVDJCyyUhW2A9i5ByfRWuLnn4bq9qsTyNoaMQ+ evQuN+DSNiDmjvIPaNBuEzk98gnV7Uop7f07H90YXVBZM5keDgvLn0E57s5hTDN0XS qMakyJlU8RDCkIxUEnH7f/aJ97QbH+NWsSKqGUiBMvxVGwHjjtr/nmmwjvp7M+RraC HBA/OzySlqFI2j3k6XwdIp46QO5jKNJoNMC4fKzMYtFBApCwa+TKrSvGFsbxtppyks /SQ0cycO0AlcTfTivNZLyshR9FeH9e8z93UZjbLE1pgt0SydDZ5eP4CB1xMgNEoeLO dQI3JybRGk0CA== From: Jakub Kicinski To: davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, Jakub Kicinski , dsahern@kernel.org Subject: [PATCH net] ipv6: fix NULL pointer deref in ip6_rt_get_dev_rcu() Date: Sun, 1 Mar 2026 11:45:48 -0800 Message-ID: <20260301194548.927324-1-kuba@kernel.org> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit l3mdev_master_dev_rcu() can return NULL when the slave device is being un-slaved from a VRF. All other callers deal with this, but we lost the fallback to loopback in ip6_rt_pcpu_alloc() -> ip6_rt_get_dev_rcu() with commit 4832c30d5458 ("net: ipv6: put host and anycast routes on device with address"). KASAN: null-ptr-deref in range [0x0000000000000108-0x000000000000010f] RIP: 0010:ip6_rt_pcpu_alloc (net/ipv6/route.c:1418) Call Trace: ip6_pol_route (net/ipv6/route.c:2318) fib6_rule_lookup (net/ipv6/fib6_rules.c:115) ip6_route_output_flags (net/ipv6/route.c:2607) vrf_process_v6_outbound (drivers/net/vrf.c:437) I was tempted to rework the un-slaving code to clear the flag first and insert synchronize_rcu() before we remove the upper. But looks like the explicit fallback to loopback_dev is an established pattern. And I guess avoiding the synchronize_rcu() is nice, too. Fixes: 4832c30d5458 ("net: ipv6: put host and anycast routes on device with address") Signed-off-by: Jakub Kicinski --- now that NIPA is not full of the tc-action.sh crashes this 1 in ~30 runs crash in fcnal_ipv6.sh pops out quite clearly. CC: dsahern@kernel.org --- net/ipv6/route.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 85df25c36409..7db0c837196c 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1063,7 +1063,8 @@ static struct net_device *ip6_rt_get_dev_rcu(const struct fib6_result *res) */ if (netif_is_l3_slave(dev) && !rt6_need_strict(&res->f6i->fib6_dst.addr)) - dev = l3mdev_master_dev_rcu(dev); + dev = l3mdev_master_dev_rcu(dev) ? : + dev_net(dev)->loopback_dev; else if (!netif_is_l3_master(dev)) dev = dev_net(dev)->loopback_dev; /* last case is netif_is_l3_master(dev) is true in which -- 2.53.0