From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793214450; b=1uWwO9usXEV0hyEaFK/2A9ejp1WSFAufecNqfvnKEIQyW2ruVlTCtAO4QbqUYE+WFLou /yP9erIRjAIxnz/H61muvf+T5cQafyOUq66zwPCKSvwmnfHEWINYKN+KkSK8feRuG2KRD Hmi4jqCeZKj7XbEcbr+Q4UJ/rIF2IWR2QiZR/tIEKbq3H77nbbsy4ce93pAWz6ok/fytm wkc5UyKSb5zlYCQmAdhR5tb730xum1pFbPNx9JIVr1qJTyV7O4Ecb6ZvSN7PoiET1oooT /ZFqBks2DPzLHGnikDmi/33Lt/P7SyOHitlNyrlcpsSipgR/jaxxRWDdX61acZ/lE1A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793214450; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=1ERfc572c/Z4+ti3JlWY5vXexgamX9v9x/s/Iv4cDwY=; b=iDzgIPQl+8WnDxrLkBniC1jlDIpfKftq0FzxHkgGmbpv2bqFOH4EF5+EB6Nw88lAMBoK PpwATWxfkUd4PIpYLHi6OLtM1+kRRQLYdIsf8EEUmCMkJIAoCZY1uD/eVfELzLEDsLjrK yPO+Cxhu/lqdDKZw145SMgMGktkzARL8F+IecEbl4UAf2heRf3nGzOnlbm7+RNN4O654j Al1T7m8htXIM8rKnQNkm5W7NAdU5zdrjoOJDtGuFp4vMph13P9w9Q6Cihalb5aLIAfUBb d4dOJv1LiaKM6+9qsUCgMxoiyJ6Av9oXCxZK+1NT62TWHEkAnNyX0NhFchNTfR3okJg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=N12iW7LO; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 98B49606BFAD; Wed, 28 Oct 2026 19:07:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=N12iW7LO Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAB041F01825; Wed, 28 Oct 2026 19:07:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793214450; bh=1ERfc572c/Z4+ti3JlWY5vXexgamX9v9x/s/Iv4cDwY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=N12iW7LOTrLbx5dG/coFTPKnBt61IGVWaJ6Mxva1yXECbbGHCPgYVQgIAIx+lIt9b 7KvOmmV0ngYd3Hh8sZ6MYZuu1VHTyBSunN3CR38aRWpkehbDqscetIVI2wY6LqUFq5 izmDo0OQht2rTd0bbgWz0jT3YrbSVxGCbA/ExSn4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , David Ahern , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1 0864/1887] ipv6: use RCU in ip6_output() Date: Wed, 28 Oct 2026 17:49:20 +0100 Message-ID: <20261028170519.079511097@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 11709573cc4e48dc34c80fc7ab9ce5b159e29695 ] Use RCU in ip6_output() in order to use dst_dev_rcu() to prevent possible UAF. We can remove rcu_read_lock()/rcu_read_unlock() pairs from ip6_finish_output2(). Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()") Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://patch.msgid.link/20250828195823.3958522-5-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/ip6_output.c | 30 ++++++++++++++++-------------- 1 file changed, 16 insertions(+), 14 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 7ad60793c853c..3ff6f43bd40ae 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -59,7 +59,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb) { struct dst_entry *dst = skb_dst(skb); - struct net_device *dev = dst->dev; + struct net_device *dev = dst_dev_rcu(dst); struct inet6_dev *idev = ip6_dst_idev(dst); unsigned int hh_len = LL_RESERVED_SPACE(dev); const struct in6_addr *daddr, *nexthop; @@ -69,15 +69,12 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * /* Be paranoid, rather than too clever. */ if (unlikely(hh_len > skb_headroom(skb)) && dev->header_ops) { - /* Make sure idev stays alive */ - rcu_read_lock(); + /* idev stays alive because we hold rcu_read_lock(). */ skb = skb_expand_head(skb, hh_len); if (!skb) { IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS); - rcu_read_unlock(); return -ENOMEM; } - rcu_read_unlock(); } hdr = ipv6_hdr(skb); @@ -122,7 +119,6 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * daddr = &hdr->daddr; } - rcu_read_lock(); nexthop = rt6_nexthop(dst_rt6_info(dst), daddr); neigh = __ipv6_neigh_lookup_noref(dev, nexthop); @@ -130,7 +126,6 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * if (unlikely(!neigh)) neigh = __neigh_create(&nd_tbl, nexthop, dev, false); if (IS_ERR(neigh)) { - rcu_read_unlock(); IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTNOROUTES); kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_CREATEFAIL); return -EINVAL; @@ -138,7 +133,6 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * } sock_confirm_neigh(skb, neigh); ret = neigh_output(neigh, skb, false); - rcu_read_unlock(); return ret; } @@ -224,22 +218,30 @@ static int ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff *s int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb) { - struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev; - struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb)); + struct dst_entry *dst = skb_dst(skb); + struct net_device *dev, *indev = skb->dev; + struct inet6_dev *idev; + int ret; skb->protocol = htons(ETH_P_IPV6); + rcu_read_lock(); + dev = dst_dev_rcu(dst); + idev = ip6_dst_idev(dst); skb->dev = dev; if (unlikely(!idev || READ_ONCE(idev->cnf.disable_ipv6))) { IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS); + rcu_read_unlock(); kfree_skb_reason(skb, SKB_DROP_REASON_IPV6DISABLED); return 0; } - return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING, - net, sk, skb, indev, dev, - ip6_finish_output, - !(IP6CB(skb)->flags & IP6SKB_REROUTED)); + ret = NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING, + net, sk, skb, indev, dev, + ip6_finish_output, + !(IP6CB(skb)->flags & IP6SKB_REROUTED)); + rcu_read_unlock(); + return ret; } EXPORT_SYMBOL(ip6_output); -- 2.53.0