[PATCH net,v2 00/11] Netfilter/IPVS fixes for net

[PATCH net,v2 00/11] Netfilter/IPVS fixes for net

[Pablo Neira Ayuso]

v2: Keep back patches that have lengthy feedback by AI, they might
    need more work.

-o-

Hi,

The following patchset contains Netfilter/IPVS fixes for net: Mostly
addressing very old bugs in the SIP conntrack helper string parser,
unsafe arp_tables match support with legacy IEEE1394, restrict xt_realm
to IPv4 and incorrect use of RCU lists in nat core and nftables. This
batch also includes one IPVS MTU fix.

1) Fix arp_tables match with IEEE1394 ARP payload, allowing to
   reach bytes off the skb boundary, note that matching on the
   target address is deliberately ignored, patch from Weiming Shi.

2) Reject unsafe nfnetlink_osf configurations from control plane,
   this is addressing a possible division by zero, from Xiang Mei.

3) nft_osf actually only supports IPv4, restrict it.

4) Possible null-ptr-deref in nfnetlink_osf, check__in_dev_get_rcu
   return NULL, from Kito Xu.

5) Remove unsafe use of sprintf to fix possible buffer overflow
   in the SIP NAT helper, from Florian Westphal.

6) Restrict xt_mac, xt_owner and xt_physdev to inet families only;
   xt_realm is only for ipv4, otherwise null-pointer-deref is possible.

7) Use kfree_rcu() in nat core to release hooks, this can be an issue
   once nfnetlink_hook gets support to dump NAT hook information,
   not currently a real issue but better fix it now.

8) Fix MTU checks in IPVS, from Yingnan Zhang.

9) Use list_del_rcu() in chain and flowtable hook unregistration,
   concurrent RCU reader could be walking over the hook list,
   from Florian Westphal

10) Add list_splice_rcu(), this is required to fix unsafe
    splice to RCU protected hook list. Reviewed by Paul McKenney.

11) Use list_splice_rcu() to splice new chain and flowtable hooks.

Please, pull these changes from:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git nf-26-04-16

Thanks.

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

The following changes since commit 2dddb34dd0d07b01fa770eca89480a4da4f13153:

  net: ethernet: mtk_eth_soc: initialize PPE per-tag-layer MTU registers (2026-04-12 15:22:58 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git tags/nf-26-04-16

for you to fetch changes up to 985f517db19a734d4267e003438b5d6995669aff:

  netfilter: nf_tables: join hook list via splice_list_rcu() in commit phase (2026-04-16 14:53:52 +0200)

----------------------------------------------------------------
netfilter pull request 26-04-16

----------------------------------------------------------------
Florian Westphal (2):
      netfilter: conntrack: remove sprintf usage
      netfilter: nf_tables: use list_del_rcu for netlink hooks

Kito Xu (veritas501) (1):
      netfilter: nfnetlink_osf: fix null-ptr-deref in nf_osf_ttl

Pablo Neira Ayuso (5):
      netfilter: nft_osf: restrict it to ipv4
      netfilter: xtables: restrict several matches to inet family
      netfilter: nat: use kfree_rcu to release ops
      rculist: add list_splice_rcu() for private lists
      netfilter: nf_tables: join hook list via splice_list_rcu() in commit phase

Weiming Shi (1):
      netfilter: arp_tables: fix IEEE1394 ARP payload parsing in arp_packet_match()

Xiang Mei (1):
      netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO

Yingnan Zhang (1):
      ipvs: fix MTU check for GSO packets in tunnel mode

 include/linux/rculist.h           | 29 ++++++++++++++++++++++
 net/ipv4/netfilter/arp_tables.c   | 14 ++++++++---
 net/ipv4/netfilter/iptable_nat.c  |  2 +-
 net/ipv6/netfilter/ip6table_nat.c |  2 +-
 net/netfilter/ipvs/ip_vs_xmit.c   | 19 +++++++++++---
 net/netfilter/nf_nat_amanda.c     |  2 +-
 net/netfilter/nf_nat_core.c       | 10 +++++---
 net/netfilter/nf_nat_sip.c        | 33 ++++++++++++++-----------
 net/netfilter/nf_tables_api.c     | 52 +++++++++++++++++----------------------
 net/netfilter/nfnetlink_osf.c     |  7 ++++++
 net/netfilter/nft_osf.c           |  6 ++++-
 net/netfilter/xt_mac.c            | 34 ++++++++++++++++---------
 net/netfilter/xt_owner.c          | 37 +++++++++++++++++++---------
 net/netfilter/xt_physdev.c        | 29 ++++++++++++++--------
 net/netfilter/xt_realm.c          |  2 +-
 15 files changed, 184 insertions(+), 94 deletions(-)

[PATCH net 01/11] netfilter: arp_tables: fix IEEE1394 ARP payload parsing in arp_packet_match()

[Pablo Neira Ayuso]

From: Weiming Shi <bestswngs@gmail.com>

arp_packet_match() unconditionally parses the ARP payload assuming two
hardware addresses are present (source and target). However,
IPv4-over-IEEE1394 ARP (RFC 2734) omits the target hardware address
field, and arp_hdr_len() already accounts for this by returning a
shorter length for ARPHRD_IEEE1394 devices.

As a result, on IEEE1394 interfaces arp_packet_match() advances past a
nonexistent target hardware address and reads the wrong bytes for both
the target device address comparison and the target IP address. This
causes arptables rules to match against garbage data, leading to
incorrect filtering decisions: packets that should be accepted may be
dropped and vice versa.

The ARP stack in net/ipv4/arp.c (arp_create and arp_process) already
handles this correctly by skipping the target hardware address for
ARPHRD_IEEE1394. Apply the same pattern to arp_packet_match().

[ Pablo has mangled this patch to include Simon Horman's suggestions ]

Fixes: 6752c8db8e0c ("firewire net, ipv4 arp: Extend hardware address and remove driver-level packet inspection.")
Reported-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/ipv4/netfilter/arp_tables.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 1cdd9c28ab2d..a7a56890b5b5 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -110,13 +110,21 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
 	arpptr += dev->addr_len;
 	memcpy(&src_ipaddr, arpptr, sizeof(u32));
 	arpptr += sizeof(u32);
-	tgt_devaddr = arpptr;
-	arpptr += dev->addr_len;
+
+	if (IS_ENABLED(CONFIG_FIREWIRE_NET) && dev->type == ARPHRD_IEEE1394) {
+		tgt_devaddr = NULL;
+	} else {
+		tgt_devaddr = arpptr;
+		arpptr += dev->addr_len;
+	}
 	memcpy(&tgt_ipaddr, arpptr, sizeof(u32));
 
 	if (NF_INVF(arpinfo, ARPT_INV_SRCDEVADDR,
 		    arp_devaddr_compare(&arpinfo->src_devaddr, src_devaddr,
-					dev->addr_len)) ||
+					dev->addr_len)))
+		return 0;
+
+	if (tgt_devaddr &&
 	    NF_INVF(arpinfo, ARPT_INV_TGTDEVADDR,
 		    arp_devaddr_compare(&arpinfo->tgt_devaddr, tgt_devaddr,
 					dev->addr_len)))
-- 
2.47.3

[PATCH net 02/11] netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO

[Pablo Neira Ayuso]

From: Xiang Mei <xmei5@asu.edu>

nf_osf_match_one() computes ctx->window % f->wss.val in the
OSF_WSS_MODULO branch with no guard for f->wss.val == 0. A
CAP_NET_ADMIN user can add such a fingerprint via nfnetlink; a
subsequent matching TCP SYN divides by zero and panics the kernel.

Reject the bogus fingerprint in nfnl_osf_add_callback() above the
per-option for-loop. f->wss is per-fingerprint, not per-option, so
the check must run regardless of f->opt_num (including 0). Also
reject wss.wc >= OSF_WSS_MAX; nf_osf_match_one() already treats that
as "should not happen".

Crash:
 Oops: divide error: 0000 [#1] SMP KASAN NOPTI
 RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)
 Call Trace:
 <IRQ>
  nf_osf_match (net/netfilter/nfnetlink_osf.c:220)
  xt_osf_match_packet (net/netfilter/xt_osf.c:32)
  ipt_do_table (net/ipv4/netfilter/ip_tables.c:348)
  nf_hook_slow (net/netfilter/core.c:622)
  ip_local_deliver (net/ipv4/ip_input.c:265)
  ip_rcv (include/linux/skbuff.h:1162)
  __netif_receive_skb_one_core (net/core/dev.c:6181)
  process_backlog (net/core/dev.c:6642)
  __napi_poll (net/core/dev.c:7710)
  net_rx_action (net/core/dev.c:7945)
  handle_softirqs (kernel/softirq.c:622)

Fixes: 11eeef41d5f6 ("netfilter: passive OS fingerprint xtables match")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Suggested-by: Florian Westphal <fw@strlen.de>
Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nfnetlink_osf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
index 45d9ad231a92..70172ca07858 100644
--- a/net/netfilter/nfnetlink_osf.c
+++ b/net/netfilter/nfnetlink_osf.c
@@ -320,6 +320,10 @@ static int nfnl_osf_add_callback(struct sk_buff *skb,
 	if (f->opt_num > ARRAY_SIZE(f->opt))
 		return -EINVAL;
 
+	if (f->wss.wc >= OSF_WSS_MAX ||
+	    (f->wss.wc == OSF_WSS_MODULO && f->wss.val == 0))
+		return -EINVAL;
+
 	for (i = 0; i < f->opt_num; i++) {
 		if (!f->opt[i].length || f->opt[i].length > MAX_IPOPTLEN)
 			return -EINVAL;
-- 
2.47.3

[PATCH net 03/11] netfilter: nft_osf: restrict it to ipv4

[Pablo Neira Ayuso]

This expression only supports for ipv4, restrict it.

Fixes: b96af92d6eaf ("netfilter: nf_tables: implement Passive OS fingerprint module in nft_osf")
Acked-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nft_osf.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nft_osf.c b/net/netfilter/nft_osf.c
index 1c0b493ef0a9..bdc2f6c90e2f 100644
--- a/net/netfilter/nft_osf.c
+++ b/net/netfilter/nft_osf.c
@@ -28,6 +28,11 @@ static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
 	struct nf_osf_data data;
 	struct tcphdr _tcph;
 
+	if (nft_pf(pkt) != NFPROTO_IPV4) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
 	if (pkt->tprot != IPPROTO_TCP) {
 		regs->verdict.code = NFT_BREAK;
 		return;
@@ -114,7 +119,6 @@ static int nft_osf_validate(const struct nft_ctx *ctx,
 
 	switch (ctx->family) {
 	case NFPROTO_IPV4:
-	case NFPROTO_IPV6:
 	case NFPROTO_INET:
 		hooks = (1 << NF_INET_LOCAL_IN) |
 			(1 << NF_INET_PRE_ROUTING) |
-- 
2.47.3

[PATCH net 04/11] netfilter: nfnetlink_osf: fix null-ptr-deref in nf_osf_ttl

[Pablo Neira Ayuso]

From: "Kito Xu (veritas501)" <hxzene@gmail.com>

nf_osf_ttl() calls __in_dev_get_rcu(skb->dev) and passes the result
to in_dev_for_each_ifa_rcu() without checking for NULL. When the
receiving device has no IPv4 configuration (ip_ptr is NULL),
__in_dev_get_rcu() returns NULL and in_dev_for_each_ifa_rcu()
dereferences it unconditionally, causing a kernel crash.

This can happen when a packet arrives on a device that has had its
IPv4 configuration removed (e.g., MTU set below IPV4_MIN_MTU causing
inetdev_destroy) or on a device that was never assigned an IPv4
address, while an xt_osf or nft_osf rule with TTL_LESS mode is
active and the packet TTL exceeds the fingerprint TTL.

Add a NULL check for in_dev before using it. When in_dev is NULL,
return 0 (no match) since source-address locality cannot be
determined without IPv4 addresses on the device.

KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
RIP: 0010:nf_osf_match_one+0x204/0xa70
Call Trace:
 <IRQ>
 nf_osf_match+0x2f8/0x780
 xt_osf_match_packet+0x11c/0x1f0
 ipt_do_table+0x7fe/0x12b0
 nf_hook_slow+0xac/0x1e0
 ip_rcv+0x123/0x370
 __netif_receive_skb_one_core+0x166/0x1b0
 process_backlog+0x197/0x590
 __napi_poll+0xa1/0x540
 net_rx_action+0x401/0xd80
 handle_softirqs+0x19f/0x610
 </IRQ>

Fixes: a218dc82f0b5 ("netfilter: nft_osf: Add ttl option support")
Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Kito Xu (veritas501) <hxzene@gmail.com>
Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nfnetlink_osf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
index 70172ca07858..4bbe64288b90 100644
--- a/net/netfilter/nfnetlink_osf.c
+++ b/net/netfilter/nfnetlink_osf.c
@@ -36,6 +36,9 @@ static inline int nf_osf_ttl(const struct sk_buff *skb,
 	const struct in_ifaddr *ifa;
 	int ret = 0;
 
+	if (!in_dev)
+		return 0;
+
 	if (ttl_check == NF_OSF_TTL_TRUE)
 		return ip->ttl == f_ttl;
 	if (ttl_check == NF_OSF_TTL_NOCHECK)
-- 
2.47.3

[PATCH net 05/11] netfilter: conntrack: remove sprintf usage

[Pablo Neira Ayuso]

From: Florian Westphal <fw@strlen.de>

Replace it with scnprintf, the buffer sizes are expected to be large enough
to hold the result, no need for snprintf+overflow check.

Increase buffer size in mangle_content_len() while at it.

BUG: KASAN: stack-out-of-bounds in vsnprintf+0xea5/0x1270
Write of size 1 at addr [..]
 vsnprintf+0xea5/0x1270
 sprintf+0xb1/0xe0
 mangle_content_len+0x1ac/0x280
 nf_nat_sdp_session+0x1cc/0x240
 process_sdp+0x8f8/0xb80
 process_invite_request+0x108/0x2b0
 process_sip_msg+0x5da/0xf50
 sip_help_tcp+0x45e/0x780
 nf_confirm+0x34d/0x990
 [..]

Fixes: 9fafcd7b2032 ("[NETFILTER]: nf_conntrack/nf_nat: add SIP helper port")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_nat_amanda.c |  2 +-
 net/netfilter/nf_nat_sip.c    | 33 ++++++++++++++++++---------------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/net/netfilter/nf_nat_amanda.c b/net/netfilter/nf_nat_amanda.c
index 98deef6cde69..8f1054920a85 100644
--- a/net/netfilter/nf_nat_amanda.c
+++ b/net/netfilter/nf_nat_amanda.c
@@ -50,7 +50,7 @@ static unsigned int help(struct sk_buff *skb,
 		return NF_DROP;
 	}
 
-	sprintf(buffer, "%u", port);
+	snprintf(buffer, sizeof(buffer), "%u", port);
 	if (!nf_nat_mangle_udp_packet(skb, exp->master, ctinfo,
 				      protoff, matchoff, matchlen,
 				      buffer, strlen(buffer))) {
diff --git a/net/netfilter/nf_nat_sip.c b/net/netfilter/nf_nat_sip.c
index cf4aeb299bde..c845b6d1a2bd 100644
--- a/net/netfilter/nf_nat_sip.c
+++ b/net/netfilter/nf_nat_sip.c
@@ -68,25 +68,27 @@ static unsigned int mangle_packet(struct sk_buff *skb, unsigned int protoff,
 }
 
 static int sip_sprintf_addr(const struct nf_conn *ct, char *buffer,
+			    size_t size,
 			    const union nf_inet_addr *addr, bool delim)
 {
 	if (nf_ct_l3num(ct) == NFPROTO_IPV4)
-		return sprintf(buffer, "%pI4", &addr->ip);
+		return scnprintf(buffer, size, "%pI4", &addr->ip);
 	else {
 		if (delim)
-			return sprintf(buffer, "[%pI6c]", &addr->ip6);
+			return scnprintf(buffer, size, "[%pI6c]", &addr->ip6);
 		else
-			return sprintf(buffer, "%pI6c", &addr->ip6);
+			return scnprintf(buffer, size, "%pI6c", &addr->ip6);
 	}
 }
 
 static int sip_sprintf_addr_port(const struct nf_conn *ct, char *buffer,
+				 size_t size,
 				 const union nf_inet_addr *addr, u16 port)
 {
 	if (nf_ct_l3num(ct) == NFPROTO_IPV4)
-		return sprintf(buffer, "%pI4:%u", &addr->ip, port);
+		return scnprintf(buffer, size, "%pI4:%u", &addr->ip, port);
 	else
-		return sprintf(buffer, "[%pI6c]:%u", &addr->ip6, port);
+		return scnprintf(buffer, size, "[%pI6c]:%u", &addr->ip6, port);
 }
 
 static int map_addr(struct sk_buff *skb, unsigned int protoff,
@@ -119,7 +121,7 @@ static int map_addr(struct sk_buff *skb, unsigned int protoff,
 	if (nf_inet_addr_cmp(&newaddr, addr) && newport == port)
 		return 1;
 
-	buflen = sip_sprintf_addr_port(ct, buffer, &newaddr, ntohs(newport));
+	buflen = sip_sprintf_addr_port(ct, buffer, sizeof(buffer), &newaddr, ntohs(newport));
 	return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 			     matchoff, matchlen, buffer, buflen);
 }
@@ -212,7 +214,7 @@ static unsigned int nf_nat_sip(struct sk_buff *skb, unsigned int protoff,
 					       &addr, true) > 0 &&
 		    nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.src.u3) &&
 		    !nf_inet_addr_cmp(&addr, &ct->tuplehash[!dir].tuple.dst.u3)) {
-			buflen = sip_sprintf_addr(ct, buffer,
+			buflen = sip_sprintf_addr(ct, buffer, sizeof(buffer),
 					&ct->tuplehash[!dir].tuple.dst.u3,
 					true);
 			if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
@@ -229,7 +231,7 @@ static unsigned int nf_nat_sip(struct sk_buff *skb, unsigned int protoff,
 					       &addr, false) > 0 &&
 		    nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.dst.u3) &&
 		    !nf_inet_addr_cmp(&addr, &ct->tuplehash[!dir].tuple.src.u3)) {
-			buflen = sip_sprintf_addr(ct, buffer,
+			buflen = sip_sprintf_addr(ct, buffer, sizeof(buffer),
 					&ct->tuplehash[!dir].tuple.src.u3,
 					false);
 			if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
@@ -247,7 +249,7 @@ static unsigned int nf_nat_sip(struct sk_buff *skb, unsigned int protoff,
 		    htons(n) == ct->tuplehash[dir].tuple.dst.u.udp.port &&
 		    htons(n) != ct->tuplehash[!dir].tuple.src.u.udp.port) {
 			__be16 p = ct->tuplehash[!dir].tuple.src.u.udp.port;
-			buflen = sprintf(buffer, "%u", ntohs(p));
+			buflen = scnprintf(buffer, sizeof(buffer), "%u", ntohs(p));
 			if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 					   poff, plen, buffer, buflen)) {
 				nf_ct_helper_log(skb, ct, "cannot mangle rport");
@@ -418,7 +420,8 @@ static unsigned int nf_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
 
 	if (!nf_inet_addr_cmp(&exp->tuple.dst.u3, &exp->saved_addr) ||
 	    exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) {
-		buflen = sip_sprintf_addr_port(ct, buffer, &newaddr, port);
+		buflen = sip_sprintf_addr_port(ct, buffer, sizeof(buffer),
+					       &newaddr, port);
 		if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 				   matchoff, matchlen, buffer, buflen)) {
 			nf_ct_helper_log(skb, ct, "cannot mangle packet");
@@ -438,8 +441,8 @@ static int mangle_content_len(struct sk_buff *skb, unsigned int protoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
+	char buffer[sizeof("4294967295")];
 	unsigned int matchoff, matchlen;
-	char buffer[sizeof("65536")];
 	int buflen, c_len;
 
 	/* Get actual SDP length */
@@ -454,7 +457,7 @@ static int mangle_content_len(struct sk_buff *skb, unsigned int protoff,
 			      &matchoff, &matchlen) <= 0)
 		return 0;
 
-	buflen = sprintf(buffer, "%u", c_len);
+	buflen = scnprintf(buffer, sizeof(buffer), "%u", c_len);
 	return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 			     matchoff, matchlen, buffer, buflen);
 }
@@ -491,7 +494,7 @@ static unsigned int nf_nat_sdp_addr(struct sk_buff *skb, unsigned int protoff,
 	char buffer[INET6_ADDRSTRLEN];
 	unsigned int buflen;
 
-	buflen = sip_sprintf_addr(ct, buffer, addr, false);
+	buflen = sip_sprintf_addr(ct, buffer, sizeof(buffer), addr, false);
 	if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen,
 			      sdpoff, type, term, buffer, buflen))
 		return 0;
@@ -509,7 +512,7 @@ static unsigned int nf_nat_sdp_port(struct sk_buff *skb, unsigned int protoff,
 	char buffer[sizeof("nnnnn")];
 	unsigned int buflen;
 
-	buflen = sprintf(buffer, "%u", port);
+	buflen = scnprintf(buffer, sizeof(buffer), "%u", port);
 	if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 			   matchoff, matchlen, buffer, buflen))
 		return 0;
@@ -529,7 +532,7 @@ static unsigned int nf_nat_sdp_session(struct sk_buff *skb, unsigned int protoff
 	unsigned int buflen;
 
 	/* Mangle session description owner and contact addresses */
-	buflen = sip_sprintf_addr(ct, buffer, addr, false);
+	buflen = sip_sprintf_addr(ct, buffer, sizeof(buffer), addr, false);
 	if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen, sdpoff,
 			      SDP_HDR_OWNER, SDP_HDR_MEDIA, buffer, buflen))
 		return 0;
-- 
2.47.3

[PATCH net 06/11] netfilter: xtables: restrict several matches to inet family

[Pablo Neira Ayuso]

This is a partial revert of:

  commit ab4f21e6fb1c ("netfilter: xtables: use NFPROTO_UNSPEC in more extensions")

to allow ipv4 and ipv6 only.

- xt_mac
- xt_owner
- xt_physdev

These extensions are not used by ebtables in userspace.

Moreover, xt_realm is only for ipv4, since dst->tclassid is ipv4
specific.

Fixes: ab4f21e6fb1c ("netfilter: xtables: use NFPROTO_UNSPEC in more extensions")
Reported-by: "Kito Xu (veritas501)" <hxzene@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/xt_mac.c     | 34 +++++++++++++++++++++++-----------
 net/netfilter/xt_owner.c   | 37 +++++++++++++++++++++++++------------
 net/netfilter/xt_physdev.c | 29 +++++++++++++++++++----------
 net/netfilter/xt_realm.c   |  2 +-
 4 files changed, 68 insertions(+), 34 deletions(-)

diff --git a/net/netfilter/xt_mac.c b/net/netfilter/xt_mac.c
index 81649da57ba5..bd2354760895 100644
--- a/net/netfilter/xt_mac.c
+++ b/net/netfilter/xt_mac.c
@@ -38,25 +38,37 @@ static bool mac_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	return ret;
 }
 
-static struct xt_match mac_mt_reg __read_mostly = {
-	.name      = "mac",
-	.revision  = 0,
-	.family    = NFPROTO_UNSPEC,
-	.match     = mac_mt,
-	.matchsize = sizeof(struct xt_mac_info),
-	.hooks     = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_IN) |
-	             (1 << NF_INET_FORWARD),
-	.me        = THIS_MODULE,
+static struct xt_match mac_mt_reg[] __read_mostly = {
+	{
+		.name		= "mac",
+		.family		= NFPROTO_IPV4,
+		.match		= mac_mt,
+		.matchsize	= sizeof(struct xt_mac_info),
+		.hooks		= (1 << NF_INET_PRE_ROUTING) |
+				  (1 << NF_INET_LOCAL_IN) |
+				  (1 << NF_INET_FORWARD),
+		.me		= THIS_MODULE,
+	},
+	{
+		.name		= "mac",
+		.family		= NFPROTO_IPV6,
+		.match		= mac_mt,
+		.matchsize	= sizeof(struct xt_mac_info),
+		.hooks		= (1 << NF_INET_PRE_ROUTING) |
+				  (1 << NF_INET_LOCAL_IN) |
+				  (1 << NF_INET_FORWARD),
+		.me		= THIS_MODULE,
+	},
 };
 
 static int __init mac_mt_init(void)
 {
-	return xt_register_match(&mac_mt_reg);
+	return xt_register_matches(mac_mt_reg, ARRAY_SIZE(mac_mt_reg));
 }
 
 static void __exit mac_mt_exit(void)
 {
-	xt_unregister_match(&mac_mt_reg);
+	xt_unregister_matches(mac_mt_reg, ARRAY_SIZE(mac_mt_reg));
 }
 
 module_init(mac_mt_init);
diff --git a/net/netfilter/xt_owner.c b/net/netfilter/xt_owner.c
index 50332888c8d2..7be2fe22b067 100644
--- a/net/netfilter/xt_owner.c
+++ b/net/netfilter/xt_owner.c
@@ -127,26 +127,39 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	return true;
 }
 
-static struct xt_match owner_mt_reg __read_mostly = {
-	.name       = "owner",
-	.revision   = 1,
-	.family     = NFPROTO_UNSPEC,
-	.checkentry = owner_check,
-	.match      = owner_mt,
-	.matchsize  = sizeof(struct xt_owner_match_info),
-	.hooks      = (1 << NF_INET_LOCAL_OUT) |
-	              (1 << NF_INET_POST_ROUTING),
-	.me         = THIS_MODULE,
+static struct xt_match owner_mt_reg[] __read_mostly = {
+	{
+		.name       = "owner",
+		.revision   = 1,
+		.family     = NFPROTO_IPV4,
+		.checkentry = owner_check,
+		.match      = owner_mt,
+		.matchsize  = sizeof(struct xt_owner_match_info),
+		.hooks      = (1 << NF_INET_LOCAL_OUT) |
+			      (1 << NF_INET_POST_ROUTING),
+		.me         = THIS_MODULE,
+	},
+	{
+		.name       = "owner",
+		.revision   = 1,
+		.family     = NFPROTO_IPV6,
+		.checkentry = owner_check,
+		.match      = owner_mt,
+		.matchsize  = sizeof(struct xt_owner_match_info),
+		.hooks      = (1 << NF_INET_LOCAL_OUT) |
+			      (1 << NF_INET_POST_ROUTING),
+		.me         = THIS_MODULE,
+	}
 };
 
 static int __init owner_mt_init(void)
 {
-	return xt_register_match(&owner_mt_reg);
+	return xt_register_matches(owner_mt_reg, ARRAY_SIZE(owner_mt_reg));
 }
 
 static void __exit owner_mt_exit(void)
 {
-	xt_unregister_match(&owner_mt_reg);
+	xt_unregister_matches(owner_mt_reg, ARRAY_SIZE(owner_mt_reg));
 }
 
 module_init(owner_mt_init);
diff --git a/net/netfilter/xt_physdev.c b/net/netfilter/xt_physdev.c
index 343e65f377d4..130842c35c6f 100644
--- a/net/netfilter/xt_physdev.c
+++ b/net/netfilter/xt_physdev.c
@@ -115,24 +115,33 @@ static int physdev_mt_check(const struct xt_mtchk_param *par)
 	return 0;
 }
 
-static struct xt_match physdev_mt_reg __read_mostly = {
-	.name       = "physdev",
-	.revision   = 0,
-	.family     = NFPROTO_UNSPEC,
-	.checkentry = physdev_mt_check,
-	.match      = physdev_mt,
-	.matchsize  = sizeof(struct xt_physdev_info),
-	.me         = THIS_MODULE,
+static struct xt_match physdev_mt_reg[] __read_mostly = {
+	{
+		.name		= "physdev",
+		.family		= NFPROTO_IPV4,
+		.checkentry	= physdev_mt_check,
+		.match		= physdev_mt,
+		.matchsize	= sizeof(struct xt_physdev_info),
+		.me		= THIS_MODULE,
+	},
+	{
+		.name		= "physdev",
+		.family		= NFPROTO_IPV6,
+		.checkentry	= physdev_mt_check,
+		.match		= physdev_mt,
+		.matchsize	= sizeof(struct xt_physdev_info),
+		.me		= THIS_MODULE,
+	},
 };
 
 static int __init physdev_mt_init(void)
 {
-	return xt_register_match(&physdev_mt_reg);
+	return xt_register_matches(physdev_mt_reg, ARRAY_SIZE(physdev_mt_reg));
 }
 
 static void __exit physdev_mt_exit(void)
 {
-	xt_unregister_match(&physdev_mt_reg);
+	xt_unregister_matches(physdev_mt_reg, ARRAY_SIZE(physdev_mt_reg));
 }
 
 module_init(physdev_mt_init);
diff --git a/net/netfilter/xt_realm.c b/net/netfilter/xt_realm.c
index 6df485f4403d..61b2f1e58d15 100644
--- a/net/netfilter/xt_realm.c
+++ b/net/netfilter/xt_realm.c
@@ -33,7 +33,7 @@ static struct xt_match realm_mt_reg __read_mostly = {
 	.matchsize	= sizeof(struct xt_realm_info),
 	.hooks		= (1 << NF_INET_POST_ROUTING) | (1 << NF_INET_FORWARD) |
 			  (1 << NF_INET_LOCAL_OUT) | (1 << NF_INET_LOCAL_IN),
-	.family		= NFPROTO_UNSPEC,
+	.family		= NFPROTO_IPV4,
 	.me		= THIS_MODULE
 };
 
-- 
2.47.3

[PATCH net 07/11] netfilter: nat: use kfree_rcu to release ops

[Pablo Neira Ayuso]

Florian Westphal says:

"Historically this is not an issue, even for normal base hooks: the data
path doesn't use the original nf_hook_ops that are used to register the
callbacks.

However, in v5.14 I added the ability to dump the active netfilter
hooks from userspace.

This code will peek back into the nf_hook_ops that are available
at the tail of the pointer-array blob used by the datapath.

The nat hooks are special, because they are called indirectly from
the central nat dispatcher hook. They are currently invisible to
the nfnl hook dump subsystem though.

But once that changes the nat ops structures have to be deferred too."

Update nf_nat_register_fn() to deal with partial exposition of the hooks
from error path which can be also an issue for nfnetlink_hook.

Fixes: e2cf17d3774c ("netfilter: add new hook nfnl subsystem")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/ipv4/netfilter/iptable_nat.c  |  2 +-
 net/ipv6/netfilter/ip6table_nat.c |  2 +-
 net/netfilter/nf_nat_core.c       | 10 ++++++----
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/netfilter/iptable_nat.c b/net/ipv4/netfilter/iptable_nat.c
index a5db7c67d61b..3b1de7f82bf8 100644
--- a/net/ipv4/netfilter/iptable_nat.c
+++ b/net/ipv4/netfilter/iptable_nat.c
@@ -100,7 +100,7 @@ static void ipt_nat_unregister_lookups(struct net *net)
 	for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++)
 		nf_nat_ipv4_unregister_fn(net, &ops[i]);
 
-	kfree(ops);
+	kfree_rcu(ops, rcu);
 }
 
 static int iptable_nat_table_init(struct net *net)
diff --git a/net/ipv6/netfilter/ip6table_nat.c b/net/ipv6/netfilter/ip6table_nat.c
index e119d4f090cc..9adfbfeaab0c 100644
--- a/net/ipv6/netfilter/ip6table_nat.c
+++ b/net/ipv6/netfilter/ip6table_nat.c
@@ -102,7 +102,7 @@ static void ip6t_nat_unregister_lookups(struct net *net)
 	for (i = 0; i < ARRAY_SIZE(nf_nat_ipv6_ops); i++)
 		nf_nat_ipv6_unregister_fn(net, &ops[i]);
 
-	kfree(ops);
+	kfree_rcu(ops, rcu);
 }
 
 static int ip6table_nat_table_init(struct net *net)
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 3b5434e4ec9c..b30ca94c2bb7 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -1228,9 +1228,11 @@ int nf_nat_register_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 		ret = nf_register_net_hooks(net, nat_ops, ops_count);
 		if (ret < 0) {
 			mutex_unlock(&nf_nat_proto_mutex);
-			for (i = 0; i < ops_count; i++)
-				kfree(nat_ops[i].priv);
-			kfree(nat_ops);
+			for (i = 0; i < ops_count; i++) {
+				priv = nat_ops[i].priv;
+				kfree_rcu(priv, rcu_head);
+			}
+			kfree_rcu(nat_ops, rcu);
 			return ret;
 		}
 
@@ -1294,7 +1296,7 @@ void nf_nat_unregister_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 		}
 
 		nat_proto_net->nat_hook_ops = NULL;
-		kfree(nat_ops);
+		kfree_rcu(nat_ops, rcu);
 	}
 unlock:
 	mutex_unlock(&nf_nat_proto_mutex);
-- 
2.47.3

[PATCH net 08/11] ipvs: fix MTU check for GSO packets in tunnel mode

[Pablo Neira Ayuso]

From: Yingnan Zhang <342144303@qq.com>

Currently, IPVS skips MTU checks for GSO packets by excluding them with
the !skb_is_gso(skb) condition. This creates problems when IPVS tunnel
mode encapsulates GSO packets with IPIP headers.

The issue manifests in two ways:

1. MTU violation after encapsulation:
   When a GSO packet passes through IPVS tunnel mode, the original MTU
   check is bypassed. After adding the IPIP tunnel header, the packet
   size may exceed the outgoing interface MTU, leading to unexpected
   fragmentation at the IP layer.

2. Fragmentation with problematic IP IDs:
   When net.ipv4.vs.pmtu_disc=1 and a GSO packet with multiple segments
   is fragmented after encapsulation, each segment gets a sequentially
   incremented IP ID (0, 1, 2, ...). This happens because:

   a) The GSO packet bypasses MTU check and gets encapsulated
   b) At __ip_finish_output, the oversized GSO packet is split into
      separate SKBs (one per segment), with IP IDs incrementing
   c) Each SKB is then fragmented again based on the actual MTU

   This sequential IP ID allocation differs from the expected behavior
   and can cause issues with fragment reassembly and packet tracking.

Fix this by properly validating GSO packets using
skb_gso_validate_network_len(). This function correctly validates
whether the GSO segments will fit within the MTU after segmentation. If
validation fails, send an ICMP Fragmentation Needed message to enable
proper PMTU discovery.

Fixes: 4cdd34084d53 ("netfilter: nf_conntrack_ipv6: improve fragmentation handling")
Signed-off-by: Yingnan Zhang <342144303@qq.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/ipvs/ip_vs_xmit.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
index 3601eb86d025..7c570f48ade2 100644
--- a/net/netfilter/ipvs/ip_vs_xmit.c
+++ b/net/netfilter/ipvs/ip_vs_xmit.c
@@ -102,6 +102,18 @@ __ip_vs_dst_check(struct ip_vs_dest *dest)
 	return dest_dst;
 }
 
+/* Based on ip_exceeds_mtu(). */
+static bool ip_vs_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
+{
+	if (skb->len <= mtu)
+		return false;
+
+	if (skb_is_gso(skb) && skb_gso_validate_network_len(skb, mtu))
+		return false;
+
+	return true;
+}
+
 static inline bool
 __mtu_check_toobig_v6(const struct sk_buff *skb, u32 mtu)
 {
@@ -111,10 +123,9 @@ __mtu_check_toobig_v6(const struct sk_buff *skb, u32 mtu)
 		 */
 		if (IP6CB(skb)->frag_max_size > mtu)
 			return true; /* largest fragment violate MTU */
-	}
-	else if (skb->len > mtu && !skb_is_gso(skb)) {
+	} else if (ip_vs_exceeds_mtu(skb, mtu))
 		return true; /* Packet size violate MTU size */
-	}
+
 	return false;
 }
 
@@ -232,7 +243,7 @@ static inline bool ensure_mtu_is_adequate(struct netns_ipvs *ipvs, int skb_af,
 			return true;
 
 		if (unlikely(ip_hdr(skb)->frag_off & htons(IP_DF) &&
-			     skb->len > mtu && !skb_is_gso(skb) &&
+			     ip_vs_exceeds_mtu(skb, mtu) &&
 			     !ip_vs_iph_icmp(ipvsh))) {
 			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 				  htonl(mtu));
-- 
2.47.3

[PATCH net 09/11] netfilter: nf_tables: use list_del_rcu for netlink hooks

[Pablo Neira Ayuso]

From: Florian Westphal <fw@strlen.de>

nft_netdev_unregister_hooks and __nft_unregister_flowtable_net_hooks need
to use list_del_rcu(), this list can be walked by concurrent dumpers.

Add a new helper and use it consistently.

Fixes: f9a43007d3f7 ("netfilter: nf_tables: double hook unregistration in netns path")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_tables_api.c | 44 ++++++++++++++---------------------
 1 file changed, 18 insertions(+), 26 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 8c42247a176c..090d4d688a33 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -374,6 +374,12 @@ static void nft_netdev_hook_free_rcu(struct nft_hook *hook)
 	call_rcu(&hook->rcu, __nft_netdev_hook_free_rcu);
 }
 
+static void nft_netdev_hook_unlink_free_rcu(struct nft_hook *hook)
+{
+	list_del_rcu(&hook->list);
+	nft_netdev_hook_free_rcu(hook);
+}
+
 static void nft_netdev_unregister_hooks(struct net *net,
 					struct list_head *hook_list,
 					bool release_netdev)
@@ -384,10 +390,8 @@ static void nft_netdev_unregister_hooks(struct net *net,
 	list_for_each_entry_safe(hook, next, hook_list, list) {
 		list_for_each_entry(ops, &hook->ops_list, list)
 			nf_unregister_net_hook(net, ops);
-		if (release_netdev) {
-			list_del(&hook->list);
-			nft_netdev_hook_free_rcu(hook);
-		}
+		if (release_netdev)
+			nft_netdev_hook_unlink_free_rcu(hook);
 	}
 }
 
@@ -2323,10 +2327,8 @@ void nf_tables_chain_destroy(struct nft_chain *chain)
 
 		if (nft_base_chain_netdev(table->family, basechain->ops.hooknum)) {
 			list_for_each_entry_safe(hook, next,
-						 &basechain->hook_list, list) {
-				list_del_rcu(&hook->list);
-				nft_netdev_hook_free_rcu(hook);
-			}
+						 &basechain->hook_list, list)
+				nft_netdev_hook_unlink_free_rcu(hook);
 		}
 		module_put(basechain->type->owner);
 		if (rcu_access_pointer(basechain->stats)) {
@@ -3026,6 +3028,7 @@ static int nf_tables_updchain(struct nft_ctx *ctx, u8 genmask, u8 policy,
 				list_for_each_entry(ops, &h->ops_list, list)
 					nf_unregister_net_hook(ctx->net, ops);
 			}
+			/* hook.list is on stack, no need for list_del_rcu() */
 			list_del(&h->list);
 			nft_netdev_hook_free_rcu(h);
 		}
@@ -8903,10 +8906,8 @@ static void __nft_unregister_flowtable_net_hooks(struct net *net,
 	list_for_each_entry_safe(hook, next, hook_list, list) {
 		list_for_each_entry(ops, &hook->ops_list, list)
 			nft_unregister_flowtable_ops(net, flowtable, ops);
-		if (release_netdev) {
-			list_del(&hook->list);
-			nft_netdev_hook_free_rcu(hook);
-		}
+		if (release_netdev)
+			nft_netdev_hook_unlink_free_rcu(hook);
 	}
 }
 
@@ -8977,8 +8978,7 @@ static int nft_register_flowtable_net_hooks(struct net *net,
 
 			nft_unregister_flowtable_ops(net, flowtable, ops);
 		}
-		list_del_rcu(&hook->list);
-		nft_netdev_hook_free_rcu(hook);
+		nft_netdev_hook_unlink_free_rcu(hook);
 	}
 
 	return err;
@@ -8988,10 +8988,8 @@ static void nft_hooks_destroy(struct list_head *hook_list)
 {
 	struct nft_hook *hook, *next;
 
-	list_for_each_entry_safe(hook, next, hook_list, list) {
-		list_del_rcu(&hook->list);
-		nft_netdev_hook_free_rcu(hook);
-	}
+	list_for_each_entry_safe(hook, next, hook_list, list)
+		nft_netdev_hook_unlink_free_rcu(hook);
 }
 
 static int nft_flowtable_update(struct nft_ctx *ctx, const struct nlmsghdr *nlh,
@@ -9079,8 +9077,7 @@ static int nft_flowtable_update(struct nft_ctx *ctx, const struct nlmsghdr *nlh,
 				nft_unregister_flowtable_ops(ctx->net,
 							     flowtable, ops);
 		}
-		list_del_rcu(&hook->list);
-		nft_netdev_hook_free_rcu(hook);
+		nft_netdev_hook_unlink_free_rcu(hook);
 	}
 
 	return err;
@@ -9586,13 +9583,8 @@ static void nf_tables_flowtable_notify(struct nft_ctx *ctx,
 
 static void nf_tables_flowtable_destroy(struct nft_flowtable *flowtable)
 {
-	struct nft_hook *hook, *next;
-
 	flowtable->data.type->free(&flowtable->data);
-	list_for_each_entry_safe(hook, next, &flowtable->hook_list, list) {
-		list_del_rcu(&hook->list);
-		nft_netdev_hook_free_rcu(hook);
-	}
+	nft_hooks_destroy(&flowtable->hook_list);
 	kfree(flowtable->name);
 	module_put(flowtable->data.type->owner);
 	kfree(flowtable);
-- 
2.47.3

[PATCH net 10/11] rculist: add list_splice_rcu() for private lists

[Pablo Neira Ayuso]

This patch adds a helper function, list_splice_rcu(), to safely splice
a private (non-RCU-protected) list into an RCU-protected list.

The function ensures that only the pointer visible to RCU readers
(prev->next) is updated using rcu_assign_pointer(), while the rest of
the list manipulations are performed with regular assignments, as the
source list is private and not visible to concurrent RCU readers.

This is useful for moving elements from a private list into a global
RCU-protected list, ensuring safe publication for RCU readers.
Subsystems with some sort of batching mechanism from userspace can
benefit from this new function.

The function __list_splice_rcu() has been added for clarity and to
follow the same pattern as in the existing list_splice*() interfaces,
where there is a check to ensure that the list to splice is not
empty. Note that __list_splice_rcu() has no documentation for this
reason.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/linux/rculist.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 2abba7552605..e3bc44225692 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -261,6 +261,35 @@ static inline void list_replace_rcu(struct list_head *old,
 	old->prev = LIST_POISON2;
 }
 
+static inline void __list_splice_rcu(struct list_head *list,
+				     struct list_head *prev,
+				     struct list_head *next)
+{
+	struct list_head *first = list->next;
+	struct list_head *last = list->prev;
+
+	last->next = next;
+	first->prev = prev;
+	next->prev = last;
+	rcu_assign_pointer(list_next_rcu(prev), first);
+}
+
+/**
+ * list_splice_rcu - splice a non-RCU list into an RCU-protected list,
+ *                   designed for stacks.
+ * @list:	the non RCU-protected list to splice
+ * @head:	the place in the existing RCU-protected list to splice
+ *
+ * The list pointed to by @head can be RCU-read traversed concurrently with
+ * this function.
+ */
+static inline void list_splice_rcu(struct list_head *list,
+				   struct list_head *head)
+{
+	if (!list_empty(list))
+		__list_splice_rcu(list, head, head->next);
+}
+
 /**
  * __list_splice_init_rcu - join an RCU-protected list into an existing list.
  * @list:	the RCU-protected list to splice
-- 
2.47.3

[PATCH net 11/11] netfilter: nf_tables: join hook list via splice_list_rcu() in commit phase

[Pablo Neira Ayuso]

Publish new hooks in the list into the basechain/flowtable using
splice_list_rcu() to ensure netlink dump list traversal via rcu is safe
while concurrent ruleset update is going on.

Fixes: 78d9f48f7f44 ("netfilter: nf_tables: add devices to existing flowtable")
Fixes: b9703ed44ffb ("netfilter: nf_tables: support for adding new devices to an existing netdev chain")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_tables_api.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 090d4d688a33..8c0706d6d887 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -10904,8 +10904,8 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 				nft_chain_commit_update(nft_trans_container_chain(trans));
 				nf_tables_chain_notify(&ctx, NFT_MSG_NEWCHAIN,
 						       &nft_trans_chain_hooks(trans));
-				list_splice(&nft_trans_chain_hooks(trans),
-					    &nft_trans_basechain(trans)->hook_list);
+				list_splice_rcu(&nft_trans_chain_hooks(trans),
+						&nft_trans_basechain(trans)->hook_list);
 				/* trans destroyed after rcu grace period */
 			} else {
 				nft_chain_commit_drop_policy(nft_trans_container_chain(trans));
@@ -11034,8 +11034,8 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 							   nft_trans_flowtable(trans),
 							   &nft_trans_flowtable_hooks(trans),
 							   NFT_MSG_NEWFLOWTABLE);
-				list_splice(&nft_trans_flowtable_hooks(trans),
-					    &nft_trans_flowtable(trans)->hook_list);
+				list_splice_rcu(&nft_trans_flowtable_hooks(trans),
+						&nft_trans_flowtable(trans)->hook_list);
 			} else {
 				nft_clear(net, nft_trans_flowtable(trans));
 				nf_tables_flowtable_notify(&ctx,
-- 
2.47.3

Re: [PATCH net,v2 00/11] Netfilter/IPVS fixes for net

[Florian Westphal]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> v2: Keep back patches that have lengthy feedback by AI, they might
>     need more work.

sashiko findings response:
  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 01/11] netfilter: arp_tables: fix IEEE1394 ARP payload parsing in arp_packet_match()

yes, arpt_mangle.c has same bug pattern, will follow up.

  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 02/11] netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO
  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 03/11] netfilter: nft_osf: restrict it to ipv4
  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 04/11] netfilter: nfnetlink_osf: fix null-ptr-deref in nf_osf_ttl

yes, osf has more issues, I asked Fernando to investigate. Brief glance
the reports are accurate but these are NOT new issues added by these 3
fixes.

 ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 07/11] netfilter: nat: use kfree_rcu to release ops

shashiko wants /kfree/kfree_rcu/ in error unwind path and I think we
should just do it.  Its an error path so it makes no practical
difference.  Also, with upcoming -next patch to dump the nat
hooks too it would be required.

  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 11/11] netfilter: nf_tables: join hook list via splice_list_rcu() in commit phase

report is accurate BUT this issue is already known and not a regression
added here.

The fix for this bug was in v1 PR but it needs more work and will come
in a followup batch.

If you don't want to take this v2 because of above issues, please
consider at least applying

  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 08/11] ipvs: fix MTU check for GSO packets in tunnel mode
  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 09/11] netfilter: nf_tables: use list_del_rcu for netlink hooks
  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 10/11] rculist: add list_splice_rcu() for private lists
  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 05/11] netfilter: conntrack: remove sprintf usage
  ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 06/11] netfilter: xtables: restrict several matches to inet family

manually.  nf:main always tracks net:main, applying them manually
doesn't cause issues.

I hope we get shashiko to also digest netfilter-devel;
otherwise this situation will persist forever or can
dissolve nf-devel and spam netdev@ directly :-|

Re: [PATCH net,v2 00/11] Netfilter/IPVS fixes for net

[Pablo Neira Ayuso]

On Thu, Apr 16, 2026 at 11:16:39PM +0200, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
[...]
> If you don't want to take this v2 because of above issues, please
> consider at least applying
> 
>   ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 08/11] ipvs: fix MTU check for GSO packets in tunnel mode
>   ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 09/11] netfilter: nf_tables: use list_del_rcu for netlink hooks
>   ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 10/11] rculist: add list_splice_rcu() for private lists
>   ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 05/11] netfilter: conntrack: remove sprintf usage
>   ↳ [2026-04-16] Pablo Neira Ayuso <pablo@netfilter.org>: [PATCH net 06/11] netfilter: xtables: restrict several matches to inet family
> 
> manually.  nf:main always tracks net:main, applying them manually
> doesn't cause issues.

Florian, I am going to prepare a v3.

Re: [PATCH net,v2 00/11] Netfilter/IPVS fixes for net

[Fernando Fernandez Mancera]

On 4/16/26 11:16 PM, Florian Westphal wrote:
[...] /* snip */
> I hope we get shashiko to also digest netfilter-devel;
> otherwise this situation will persist forever or can
> dissolve nf-devel and spam netdev@ directly :-|
> 

FWIW, I just checked that sashiko already digest 
https://lore.kernel.org/all/ - that means we can already check the 
results for netfilter-devel patches although we need to search for them 
manually.

I reached out to them so we can have a netfilter-devel filter, but I 
think we should start checking the results of sashiko on the patches 
sent to netfilter-devel by manual search.