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| author | Kyle Zeng <kylebot@openai.com> | 2026-10-07 23:01:00 +0200 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2026-10-19 14:12:26 +0200 |
| commit | 73a73d442f9986353fe284bd1b504d0313d0f153 (patch) | |
| tree | 4ddf0277ff895bb2cd08add3a6a37b80c39b6483 | |
| parent | c203ecf905745d979de5df28fa657121f2e9342d (diff) | |
| download | linux-next-73a73d442f9986353fe284bd1b504d0313d0f153.tar.gz linux-next-73a73d442f9986353fe284bd1b504d0313d0f153.zip | |
netfilter: nf_reject: initialize IPCB at inet ingress
The inet ingress hook runs before ip_rcv_core() and ip6_rcv_core(), so
neither IPCB nor IP6CB has been initialized when nft_reject_inet passes
a packet to nf_send_unreach() or nf_send_unreach6(). skb->cb can
therefore retain metadata from an earlier protocol layer.
For IPv4, icmp_send() treats IPCB(skb)->opt as parsed IPv4 options.
Stale option offsets can make __ip_options_echo() copy an
attacker-controlled length into its 40-byte reply option buffer and
overflow the stack. On an unpatched v7.2-rc5 kernel, the IPv4
reproducer produced:
BUG: KASAN: stack-out-of-bounds in __ip_options_echo()
Write of size 255
For IPv6, icmpv6_send() consumes IP6CB(skb) as parsed IPv6 metadata. It
always uses iif for source selection and, when MIP6 is enabled, uses
dsthao as an extension-header offset. These fields must not be stale.
For NF_INET_INGRESS, clear the address-family-specific control block and
restore its input interface before constructing the ICMP error. This
matches similar initialization normally performed by ip_rcv_core() and
ip6_rcv_core().
Fixes: 117ca1f8920c ("netfilter: nft_reject_inet: allow to use reject from inet ingress")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.6-sol Codex:gpt-5.5-cyber
Signed-off-by: Kyle Zeng <kylebot@openai.com>
Co-developed-by: David Lee <david.lee@trailofbits.com>
Signed-off-by: David Lee <david.lee@trailofbits.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
| -rw-r--r-- | net/ipv4/netfilter/nf_reject_ipv4.c | 5 | ||||
| -rw-r--r-- | net/ipv6/netfilter/nf_reject_ipv6.c | 5 |
2 files changed, 10 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c index 59ec465a9df9..7cb33af671e2 100644 --- a/net/ipv4/netfilter/nf_reject_ipv4.c +++ b/net/ipv4/netfilter/nf_reject_ipv4.c @@ -357,6 +357,11 @@ void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) if (!skb_valid_dst(skb_in) && nf_reject_fill_skb_dst(skb_in) < 0) return; + if (hook == NF_INET_INGRESS) { + memset(IPCB(skb_in), 0, sizeof(*IPCB(skb_in))); + IPCB(skb_in)->iif = skb_in->skb_iif; + } + if (skb_csum_unnecessary(skb_in) || !nf_reject_verify_csum(skb_in, dataoff, proto)) { icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c index 07cdaa10da0d..5e08d8529cc8 100644 --- a/net/ipv6/netfilter/nf_reject_ipv6.c +++ b/net/ipv6/netfilter/nf_reject_ipv6.c @@ -444,6 +444,11 @@ void nf_send_unreach6(struct net *net, struct sk_buff *skb_in, if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL) skb_in->dev = net->loopback_dev; + if (hooknum == NF_INET_INGRESS) { + memset(IP6CB(skb_in), 0, sizeof(*IP6CB(skb_in))); + IP6CB(skb_in)->iif = skb_in->skb_iif; + } + if (!skb_valid_dst(skb_in) && nf_reject6_fill_skb_dst(skb_in) < 0) return; |