[PATCH net 0/2] Netfilter fixes for net

[PATCH net 0/2] Netfilter fixes for net

[Pablo Neira Ayuso]

Hi,

The following patchset contains Netfilter fixes for net:

Patch #1 sets on NFT_PKTINFO_L4PROTO for UDP packets less than 4 bytes
payload from netdev/egress by subtracting skb_network_offset() when
validating IPv4 packet length, otherwise 'meta l4proto udp' never
matches.

Patch #2 subtracts skb_network_offset() when validating IPv6 packet
length for netdev/egress.

Please, pull these changes from:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git nf-24-08-28

Thanks.

----------------------------------------------------------------

The following changes since commit 8af174ea863c72f25ce31cee3baad8a301c0cf0f:

  net: mana: Fix race of mana_hwc_post_rx_wqe and new hwc response (2024-08-23 14:24:24 +0100)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git nf-24-08-28

for you to fetch changes up to 70c261d500951cf3ea0fcf32651aab9a65a91471:

  netfilter: nf_tables_ipv6: consider network offset in netdev/egress validation (2024-08-27 18:11:56 +0200)

----------------------------------------------------------------
netfilter pull request 24-08-28

----------------------------------------------------------------
Pablo Neira Ayuso (2):
      netfilter: nf_tables: restore IP sanity checks for netdev/egress
      netfilter: nf_tables_ipv6: consider network offset in netdev/egress validation

 include/net/netfilter/nf_tables_ipv4.h | 10 ++++++----
 include/net/netfilter/nf_tables_ipv6.h |  5 +++--
 2 files changed, 9 insertions(+), 6 deletions(-)

[PATCH net 1/2] netfilter: nf_tables: restore IP sanity checks for netdev/egress

[Pablo Neira Ayuso]

Subtract network offset to skb->len before performing IPv4 header sanity
checks, then adjust transport offset from offset from mac header.

Jorge Ortiz says:

When small UDP packets (< 4 bytes payload) are sent from eth0,
`meta l4proto udp` condition is not met because `NFT_PKTINFO_L4PROTO` is
not set. This happens because there is a comparison that checks if the
transport header offset exceeds the total length.  This comparison does
not take into account the fact that the skb network offset might be
non-zero in egress mode (e.g., 14 bytes for Ethernet header).

Fixes: 0ae8e4cca787 ("netfilter: nf_tables: set transport offset from mac header for netdev/egress")
Reported-by: Jorge Ortiz <jorge.ortiz.escribano@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/net/netfilter/nf_tables_ipv4.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/net/netfilter/nf_tables_ipv4.h b/include/net/netfilter/nf_tables_ipv4.h
index 60a7d0ce3080..fcf967286e37 100644
--- a/include/net/netfilter/nf_tables_ipv4.h
+++ b/include/net/netfilter/nf_tables_ipv4.h
@@ -19,7 +19,7 @@ static inline void nft_set_pktinfo_ipv4(struct nft_pktinfo *pkt)
 static inline int __nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt)
 {
 	struct iphdr *iph, _iph;
-	u32 len, thoff;
+	u32 len, thoff, skb_len;
 
 	iph = skb_header_pointer(pkt->skb, skb_network_offset(pkt->skb),
 				 sizeof(*iph), &_iph);
@@ -30,8 +30,10 @@ static inline int __nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt)
 		return -1;
 
 	len = iph_totlen(pkt->skb, iph);
-	thoff = skb_network_offset(pkt->skb) + (iph->ihl * 4);
-	if (pkt->skb->len < len)
+	thoff = iph->ihl * 4;
+	skb_len = pkt->skb->len - skb_network_offset(pkt->skb);
+
+	if (skb_len < len)
 		return -1;
 	else if (len < thoff)
 		return -1;
@@ -40,7 +42,7 @@ static inline int __nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt)
 
 	pkt->flags = NFT_PKTINFO_L4PROTO;
 	pkt->tprot = iph->protocol;
-	pkt->thoff = thoff;
+	pkt->thoff = skb_network_offset(pkt->skb) + thoff;
 	pkt->fragoff = ntohs(iph->frag_off) & IP_OFFSET;
 
 	return 0;
-- 
2.30.2

[PATCH net 2/2] netfilter: nf_tables_ipv6: consider network offset in netdev/egress validation

[Pablo Neira Ayuso]

From netdev/egress, skb->len can include the ethernet header, therefore,
subtract network offset from skb->len when validating IPv6 packet length.

Fixes: 42df6e1d221d ("netfilter: Introduce egress hook")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/net/netfilter/nf_tables_ipv6.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/net/netfilter/nf_tables_ipv6.h b/include/net/netfilter/nf_tables_ipv6.h
index 467d59b9e533..a0633eeaec97 100644
--- a/include/net/netfilter/nf_tables_ipv6.h
+++ b/include/net/netfilter/nf_tables_ipv6.h
@@ -31,8 +31,8 @@ static inline int __nft_set_pktinfo_ipv6_validate(struct nft_pktinfo *pkt)
 	struct ipv6hdr *ip6h, _ip6h;
 	unsigned int thoff = 0;
 	unsigned short frag_off;
+	u32 pkt_len, skb_len;
 	int protohdr;
-	u32 pkt_len;
 
 	ip6h = skb_header_pointer(pkt->skb, skb_network_offset(pkt->skb),
 				  sizeof(*ip6h), &_ip6h);
@@ -43,7 +43,8 @@ static inline int __nft_set_pktinfo_ipv6_validate(struct nft_pktinfo *pkt)
 		return -1;
 
 	pkt_len = ntohs(ip6h->payload_len);
-	if (pkt_len + sizeof(*ip6h) > pkt->skb->len)
+	skb_len = pkt->skb->len - skb_network_offset(pkt->skb);
+	if (pkt_len + sizeof(*ip6h) > skb_len)
 		return -1;
 
 	protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, &flags);
-- 
2.30.2

Re: [PATCH net 1/2] netfilter: nf_tables: restore IP sanity checks for netdev/egress

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Pablo Neira Ayuso <pablo@netfilter.org>:

On Wed, 28 Aug 2024 23:47:07 +0200 you wrote:
> Subtract network offset to skb->len before performing IPv4 header sanity
> checks, then adjust transport offset from offset from mac header.
> 
> Jorge Ortiz says:
> 
> When small UDP packets (< 4 bytes payload) are sent from eth0,
> `meta l4proto udp` condition is not met because `NFT_PKTINFO_L4PROTO` is
> not set. This happens because there is a comparison that checks if the
> transport header offset exceeds the total length.  This comparison does
> not take into account the fact that the skb network offset might be
> non-zero in egress mode (e.g., 14 bytes for Ethernet header).
> 
> [...]

Here is the summary with links:
  - [net,1/2] netfilter: nf_tables: restore IP sanity checks for netdev/egress
    https://git.kernel.org/netdev/net/c/5fd062891897
  - [net,2/2] netfilter: nf_tables_ipv6: consider network offset in netdev/egress validation
    https://git.kernel.org/netdev/net/c/70c261d50095

You are awesome, thank you!
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