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([192.19.161.250]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b832e4cd26sm3047244eec.12.2026.02.04.23.51.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Feb 2026 23:51:32 -0800 (PST) From: Keerthana K To: stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, kafai@fb.com, weiwan@google.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ajay.kaher@broadcom.com, alexey.makhalov@broadcom.com, vamsi-krishna.brahmajosyula@broadcom.com, yin.ding@broadcom.com, tapas.kundu@broadcom.com, Sasha Levin , Keerthana K Subject: [PATCH v6.1-v6.12 ] ipv6: use RCU in ip6_xmit() Date: Thu, 5 Feb 2026 07:47:22 +0000 Message-ID: <20260205074722.2091297-1-keerthana.kalyanasundaram@broadcom.com> X-Mailer: git-send-email 2.43.7 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e Content-Type: text/plain; charset="utf-8" From: Eric Dumazet [ Upstream commit 9085e56501d93af9f2d7bd16f7fcfacdde47b99c ] Use RCU in ip6_xmit() in order to use dst_dev_rcu() to prevent possible UAF. Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()") Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://patch.msgid.link/20250828195823.3958522-4-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Keerthana K --- net/ipv6/ip6_output.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index f7a225da8525..4ea4da0e71c9 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -258,35 +258,36 @@ bool ip6_autoflowlabel(struct net *net, const struct = ipv6_pinfo *np) int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl= 6, __u32 mark, struct ipv6_txoptions *opt, int tclass, u32 priority) { - struct net *net =3D sock_net(sk); const struct ipv6_pinfo *np =3D inet6_sk(sk); struct in6_addr *first_hop =3D &fl6->daddr; struct dst_entry *dst =3D skb_dst(skb); - struct net_device *dev =3D dst->dev; struct inet6_dev *idev =3D ip6_dst_idev(dst); struct hop_jumbo_hdr *hop_jumbo; int hoplen =3D sizeof(*hop_jumbo); + struct net *net =3D sock_net(sk); unsigned int head_room; + struct net_device *dev; struct ipv6hdr *hdr; u8 proto =3D fl6->flowi6_proto; int seg_len =3D skb->len; - int hlimit =3D -1; + int ret, hlimit =3D -1; u32 mtu; =20 + rcu_read_lock(); + + dev =3D dst_dev_rcu(dst); head_room =3D sizeof(struct ipv6hdr) + hoplen + LL_RESERVED_SPACE(dev); if (opt) head_room +=3D opt->opt_nflen + opt->opt_flen; =20 if (unlikely(head_room > skb_headroom(skb))) { - /* Make sure idev stays alive */ - rcu_read_lock(); + /* idev stays alive while we hold rcu_read_lock(). */ skb =3D skb_expand_head(skb, head_room); if (!skb) { IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS); - rcu_read_unlock(); - return -ENOBUFS; + ret =3D -ENOBUFS; + goto unlock; } - rcu_read_unlock(); } =20 if (opt) { @@ -348,17 +349,21 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *s= kb, struct flowi6 *fl6, * skb to its handler for processing */ skb =3D l3mdev_ip6_out((struct sock *)sk, skb); - if (unlikely(!skb)) - return 0; + if (unlikely(!skb)) { + ret =3D 0; + goto unlock; + } =20 /* hooks should never assume socket lock is held. * we promote our socket to non const */ - return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, - net, (struct sock *)sk, skb, NULL, dev, - dst_output); + ret =3D NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, + net, (struct sock *)sk, skb, NULL, dev, + dst_output); + goto unlock; } =20 + ret =3D -EMSGSIZE; skb->dev =3D dev; /* ipv6_local_error() does not require socket lock, * we promote our socket to non const @@ -367,7 +372,9 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb= , struct flowi6 *fl6, =20 IP6_INC_STATS(net, idev, IPSTATS_MIB_FRAGFAILS); kfree_skb(skb); - return -EMSGSIZE; +unlock: + rcu_read_unlock(); + return ret; } EXPORT_SYMBOL(ip6_xmit); =20 --=20 2.43.7