Eric Dumazet (1): ip6_gre: check tunnel info before xmit in ip6gre_tunnel_xmit Zhiling Zou (1): ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit() net/ipv6/ip6_gre.c | 6 +++++- net/ipv6/ip6_tunnel.c | 15 ++------------- 2 files changed, 7 insertions(+), 14 deletions(-) -- 2.33.8
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From: Zhiling Zou <zhilinz@nebusec.ai> stable inclusion from stable-v6.6.157 commit defa0adeff132cc90ed66915b9a104d9393e1e54 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/18891 CVE: CVE-2026-89563 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 87f21b59ddc618eff9670c174842964ad65fdade upstream. ip6_tnl_xmit() may need to expand headroom before it can push the outer IPv6 and optional encap headers. It currently does that with skb_realloc_headroom(), copies skb->sk ownership, consumes the original skb, and then continues processing with the replacement skb kept only in its local variable. That is safe only if the helper cannot fail afterwards. But this helper still has post-reallocation error exits. collect_md tunnels reject non-NONE encap after the replacement, and ip6_tnl_encap() can also fail later. In those cases the helper returns an error to its callers while the caller still only has the original skb pointer. Both ip6_tnl_start_xmit() and the IPv6 GRE paths free the caller skb on error, so they can end up freeing an skb that ip6_tnl_xmit() already consumed. Use skb_cow_head() instead. It provides the required headroom and writability without privately replacing the caller-owned skb, so later error returns cannot leave callers with a stale pointer. The Ethernet users, ip6gretap and ip6erspan, clear IFF_TX_SKB_SHARING and already call skb_cow_head() before entering ip6_tnl_xmit(). They do not rely on the removed skb_shared() reallocation. This also makes the IPv6 tunnel path consistent with ip_tunnel_xmit(). Fixes: 058214a4d1df ("ip6_tun: Add infrastructure for doing encapsulation") Cc: stable@vger.kernel.org Reported-by: Vega <vega@nebusec.ai> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai> Link: https://patch.msgid.link/30807a062ccc5c9c8a5ec2c5eb805ef279c50bdd.1786452593... Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: JiangJieHua <jiangjiehua1@huawei.com> --- net/ipv6/ip6_tunnel.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c index dfabd9969b3f3..54193e3b5492c 100644 --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -1226,19 +1226,8 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield, */ max_headroom += LL_RESERVED_SPACE(tdev); - if (skb_headroom(skb) < max_headroom || skb_shared(skb) || - (skb_cloned(skb) && !skb_clone_writable(skb, 0))) { - struct sk_buff *new_skb; - - new_skb = skb_realloc_headroom(skb, max_headroom); - if (!new_skb) - goto tx_err_dst_release; - - if (skb->sk) - skb_set_owner_w(new_skb, skb->sk); - consume_skb(skb); - skb = new_skb; - } + if (skb_cow_head(skb, max_headroom)) + goto tx_err_dst_release; if (t->parms.collect_md) { if (t->encap.type != TUNNEL_ENCAP_NONE) -- 2.33.8
From: Eric Dumazet <edumazet@google.com> mainline inclusion from mainline-v7.3-rc2 commit 97cc84dad1d7f68a36b71b69b361d88482707673 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/18891 CVE: CVE-2026-89563 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Shuangpeng Bai reported a KASAN slab-use-after-free in ip6gre_tunnel_xmit(). The precise KASAN bug was caused by ip6_tnl_xmit() consuming the skb during headroom expansion and returning an error, while ip6gre_tunnel_xmit() still held the stale pointer and called skb_tunnel_info_txcheck(skb) at tx_err. That specific bug was fixed by commit 87f21b59ddc6 ("ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()"). However, calling skb_tunnel_info_txcheck(skb) at the tx_err label after the transmission attempt remains problematic: Downstream helpers like ip6_tnl_xmit() call skb_scrub_packet(), which drops the skb's metadata_dst before transmission. If an error occurs later during transmit, inspecting skb at tx_err sees a scrubbed dst and misclassifies tx_errors vs tx_dropped. Commit e5f7e211b6aa ("ip6gre: avoid tx_error when sending MLD/DAD on external tunnels") already handled this correctly in ip6erspan_tunnel_xmit() by checking and caching tun_info before transmit. Align ip6gre_tunnel_xmit() with ip6erspan_tunnel_xmit() by caching tun_info before xmit and checking it at tx_err. Fixes: e5f7e211b6aa ("ip6gre: avoid tx_error when sending MLD/DAD on external tunnels") Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com> Closes: https://lore.kernel.org/netdev/20260819062224.3197349-1-shuangpeng.kernel@gm... Cc: Davide Caratti <dcaratti@redhat.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/20260828103731.1951815-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: JiangJieHua <jiangjiehua1@huawei.com> --- net/ipv6/ip6_gre.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 74442c9fb4abc..93937e5962f0b 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -897,6 +897,7 @@ static int ip6gre_xmit_other(struct sk_buff *skb, struct net_device *dev) static netdev_tx_t ip6gre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) { + struct ip_tunnel_info *tun_info = NULL; struct ip6_tnl *t = netdev_priv(dev); __be16 payload_protocol; int ret; @@ -907,6 +908,9 @@ static netdev_tx_t ip6gre_tunnel_xmit(struct sk_buff *skb, if (!ip6_tnl_xmit_ctl(t, &t->parms.laddr, &t->parms.raddr)) goto tx_err; + if (t->parms.collect_md) + tun_info = skb_tunnel_info_txcheck(skb); + payload_protocol = skb_protocol(skb, true); switch (payload_protocol) { case htons(ETH_P_IP): @@ -926,7 +930,7 @@ static netdev_tx_t ip6gre_tunnel_xmit(struct sk_buff *skb, return NETDEV_TX_OK; tx_err: - if (!t->parms.collect_md || !IS_ERR(skb_tunnel_info_txcheck(skb))) + if (!IS_ERR(tun_info)) DEV_STATS_INC(dev, tx_errors); DEV_STATS_INC(dev, tx_dropped); kfree_skb(skb); -- 2.33.8
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