FAILED: patch "[PATCH] netfilter: nf_tables: don't queue packet path object" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 7904b94768e983bcb2be34a8d6d1f3450f5b838b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026083157-plexiglas-pouring-6a0f@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7904b94768e983bcb2be34a8d6d1f3450f5b838b Mon Sep 17 00:00:00 2001
From: Fourie Zhang <[email protected]>
Date: Mon, 10 Aug 2026 19:35:01 +0800
Subject: [PATCH] netfilter: nf_tables: don't queue packet path object
notifications

All file:line references below are against v7.2-rc4 (ac5b0e5651b1). The trace was captured on 7.2.0-rc6-kasan72rc6 (075b74841bd0), where the same lines apply.

nft_obj_notify() is exported and reached from the packet path. Its only in-tree caller is nft_quota_obj_eval() (net/netfilter/nft_quota.c:68), which notifies with GFP_ATOMIC while evaluating a rule for a transiting packet, holding no mutex.

Since commit 67cc570edaa0 ("netfilter: nf_tables: coalesce multiple notifications into one skbuff") that notification is no longer sent immediately. __nft_obj_notify() queues it onto nft_net->notify_list via nft_notify_enqueue() (net/netfilter/nf_tables_api.c:1211), which is a bare list_add_tail(). notify_list has no lock of its own (include/net/netfilter/nf_tables.h:1951), it is serialised by commit_mutex:
the six other enqueue sites all run inside a netlink transaction, and the drain in nft_commit_notify() (net/netfilter/nf_tables_api.c:10746) does list_del() + kfree_skb() from nf_tables_commit() with commit_mutex held.

Sending packets through a chain that references a depleted quota object therefore races an unlocked list_add_tail() against list_del() + kfree_skb() on another CPU. The WRITE_ONCE(prev->next, new) in __list_add() then stores through an sk_buff that has already been freed:

  BUG: KASAN: slab-use-after-free in __nft_obj_notify+0x2c5/0x2d0
  Write of size 8 at addr ff110001047183c0 by task poc/76
  CPU: 0 UID: 1000 PID: 76 Comm: poc Tainted: G  W  7.2.0-rc6-kasan72rc6 #4
  Call Trace:
   <IRQ>
   __nft_obj_notify (include/linux/list.h:164 include/linux/list.h:191
                     net/netfilter/nf_tables_api.c:1211
                     net/netfilter/nf_tables_api.c:8743)
   nft_quota_obj_eval (net/netfilter/nft_quota.c:68)
   nft_do_chain_inet
   nf_hook_slow
   __ip_local_out
   ip_push_pending_frames
   udp_send_skb
   udp_sendmsg
   __x64_sys_sendto

  Allocated by task 77:
   __alloc_skb (net/core/skbuff.c:704)
   __nft_obj_notify (include/net/netlink.h:1055
                     net/netfilter/nf_tables_api.c:8731)
   nft_quota_obj_eval (net/netfilter/nft_quota.c:68)
   nft_do_chain

  Freed by task 79:
   nf_tables_commit (include/linux/skbuff.h:1332
                     net/netfilter/nf_tables_api.c:10759
                     net/netfilter/nf_tables_api.c:11185)
   nfnetlink_rcv_batch (net/netfilter/nfnetlink.c:574)
   netlink_unicast
   netlink_sendmsg

  The buggy address belongs to the cache skbuff_head_cache of size 232

Queueing from the packet path is wrong even leaving the race aside:
notify_list is only drained by nft_commit_notify() from nf_tables_commit() (:11185), so a notification enqueued outside a transaction is not sent until some later netlink batch commits, if one ever does.

The gfp argument that nft_obj_notify() still takes is a leftover of the pre-67cc570edaa0 behaviour, where this path called nfnetlink_send() directly. Restore that: split the message construction out into nft_obj_notify_alloc() and let each caller decide what to do with the skb. nft_obj_notify(), the exported one reached from the packet path, sends it straight away; nf_tables_obj_notify(), which runs under commit_mutex, keeps queueing it, so transaction notifications are still coalesced.

index af357f6c5070..3a7c8f7a6304 100644
@@ -8715,18 +8715,17 @@ static int nf_tables_delobj(struct sk_buff *skb, const struct nfnl_info *info,
 	return nft_delobj(&ctx, obj);
 }
 
-static void
-__nft_obj_notify(struct net *net, const struct nft_table *table,
-		 struct nft_object *obj, u32 portid, u32 seq, int event,
-		 u16 flags, int family, int report, gfp_t gfp)
+static struct sk_buff *
+nft_obj_notify_alloc(struct net *net, const struct nft_table *table,
+		     struct nft_object *obj, u32 portid, u32 seq, int event,
+		     u16 flags, int family, int report, gfp_t gfp)
 {
-	struct nftables_pernet *nft_net = nft_pernet(net);
 	struct sk_buff *skb;
 	int err;
 
 	if (!report &&
 	    !nfnetlink_has_listeners(net, NFNLGRP_NFTABLES))
-		return;
+		return NULL;
 
 	skb = nlmsg_new(NLMSG_GOODSIZE, gfp);
 	if (skb == NULL)

@@ -8740,10 +8739,10 @@ __nft_obj_notify(struct net *net, const struct nft_table *table,
 		goto err;
 	}
 
-	nft_notify_enqueue(skb, report, &nft_net->notify_list);
-	return;
+	return skb;
 err:
 	nfnetlink_set_err(net, portid, NFNLGRP_NFTABLES, -ENOBUFS);
+	return NULL;
 }
 
 void nft_obj_notify(struct net *net, const struct nft_table *table,

@@ -8752,6 +8751,7 @@ void nft_obj_notify(struct net *net, const struct nft_table *table,
 {
 	char *buf = kasprintf(gfp, "%s:%u",
 			      table->name, nft_base_seq(net));
+	struct sk_buff *skb;
 
 	audit_log_nfcfg(buf,
 			family,

@@ -8762,17 +8762,27 @@ void nft_obj_notify(struct net *net, const struct nft_table *table,
 			gfp);
 	kfree(buf);
 
-	__nft_obj_notify(net, table, obj, portid, seq, event,
-			 flags, family, report, gfp);
+	/* Called from the packet path, holding no mutex: notify_list is
+	 * serialised by commit_mutex, so send this notification directly.
+	 */
+	skb = nft_obj_notify_alloc(net, table, obj, portid, seq, event,
+				   flags, family, report, gfp);
+	if (skb)
+		nfnetlink_send(skb, net, portid, NFNLGRP_NFTABLES, report, gfp);
 }
 EXPORT_SYMBOL_GPL(nft_obj_notify);
 
 static void nf_tables_obj_notify(const struct nft_ctx *ctx,
 				 struct nft_object *obj, int event)
 {
-	__nft_obj_notify(ctx->net, ctx->table, obj, ctx->portid,
-			 ctx->seq, event, ctx->flags, ctx->family,
-			 ctx->report, GFP_KERNEL);
+	struct nftables_pernet *nft_net = nft_pernet(ctx->net);
+	struct sk_buff *skb;
+
+	skb = nft_obj_notify_alloc(ctx->net, ctx->table, obj, ctx->portid,
+				   ctx->seq, event, ctx->flags, ctx->family,
+				   ctx->report, GFP_KERNEL);
+	if (skb)
+		nft_notify_enqueue(skb, ctx->report, &nft_net->notify_list);
 }
 
 /*

From: Yang Li <[email protected]>

[ Upstream commit 67059b61597c004e23b074547b40604222bee3a0 ]

The code that uses nft_net has been removed, and the nft_pernet function is merely obtaining a reference to shared data through the net pointer. The content of the net pointer is not modified or changed, so both of them should be removed.

silence the warning:
net/netfilter/nft_set_rbtree.c:627:26: warning: variable ‘nft_net’ set but not used

[ sashal: Reduced backport -- upstream 67059b61597c0 touches 1 file(s), this
backport carries 1. Not backported here:
net/netfilter/nft_set_rbtree.c
This note is generated from the file lists only; see the resolution record for the reasoning. ]

Stable-dep-of: 7904b94768e9 ("netfilter: nf_tables: don't queue packet path object notifications")

---
 net/netfilter/nf_tables_api.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

index b6f74fa699f22..5fc2296d48c46 100644
@@ -7842,9 +7842,8 @@ void nft_obj_notify(struct net *net, const struct nft_table *table,
 		    struct nft_object *obj, u32 portid, u32 seq, int event,
 		    u16 flags, int family, int report, gfp_t gfp)
 {
-	struct nftables_pernet *nft_net = nft_pernet(net);
 	char *buf = kasprintf(gfp, "%s:%u",
-			      table->name, nft_net->base_seq);
+			      table->name, nft_base_seq(net));
 
 	audit_log_nfcfg(buf,
 			family,

2.53.0

From: Florian Westphal <[email protected]>

[ Upstream commit 64102d9bbc3d41dac5188b8fba75b1344c438970 ]

This will soon be read from packet path around same time as the gencursor.

Both gencursor and base_seq get incremented almost at the same time, so it makes sense to place them in the same structure.

This doesn't increase struct net size on 64bit due to padding.

Stable-dep-of: 7904b94768e9 ("netfilter: nf_tables: don't queue packet path object notifications")

---
 include/net/netfilter/nf_tables.h |  1 -
 include/net/netns/nftables.h      |  1 +
 net/netfilter/nf_tables_api.c     | 58 +++++++++++++++----------------
 3 files changed, 30 insertions(+), 30 deletions(-)

index e0b6c328d5377..cdd97037a1c21 100644
@@ -1753,7 +1753,6 @@ struct nftables_pernet {
 	struct mutex		commit_mutex;
 	u64			table_handle;
 	u64			tstamp;
-	unsigned int		base_seq;
 	u8			validate_state;
 	unsigned int		gc_seq;
 };

index 8c77832d02404..b9be4169317bf 100644
@@ -5,6 +5,7 @@
 #include <linux/list.h>
 
 struct netns_nftables {
+	unsigned int		base_seq;
 	u8			gencursor;
 };
 

2.53.0

From: Fourie Zhang <[email protected]>

[ Upstream commit 7904b94768e983bcb2be34a8d6d1f3450f5b838b ]

All file:line references below are against v7.2-rc4 (ac5b0e5651b1). The trace was captured on 7.2.0-rc6-kasan72rc6 (075b74841bd0), where the same lines apply.

nft_obj_notify() is exported and reached from the packet path. Its only in-tree caller is nft_quota_obj_eval() (net/netfilter/nft_quota.c:68), which notifies with GFP_ATOMIC while evaluating a rule for a transiting packet, holding no mutex.

Since commit 67cc570edaa0 ("netfilter: nf_tables: coalesce multiple notifications into one skbuff") that notification is no longer sent immediately. __nft_obj_notify() queues it onto nft_net->notify_list via nft_notify_enqueue() (net/netfilter/nf_tables_api.c:1211), which is a bare list_add_tail(). notify_list has no lock of its own (include/net/netfilter/nf_tables.h:1951), it is serialised by commit_mutex:
the six other enqueue sites all run inside a netlink transaction, and the drain in nft_commit_notify() (net/netfilter/nf_tables_api.c:10746) does list_del() + kfree_skb() from nf_tables_commit() with commit_mutex held.

Sending packets through a chain that references a depleted quota object therefore races an unlocked list_add_tail() against list_del() + kfree_skb() on another CPU. The WRITE_ONCE(prev->next, new) in __list_add() then stores through an sk_buff that has already been freed:

  BUG: KASAN: slab-use-after-free in __nft_obj_notify+0x2c5/0x2d0
  Write of size 8 at addr ff110001047183c0 by task poc/76
  CPU: 0 UID: 1000 PID: 76 Comm: poc Tainted: G  W  7.2.0-rc6-kasan72rc6 #4
  Call Trace:
   <IRQ>
   __nft_obj_notify (include/linux/list.h:164 include/linux/list.h:191
                     net/netfilter/nf_tables_api.c:1211
                     net/netfilter/nf_tables_api.c:8743)
   nft_quota_obj_eval (net/netfilter/nft_quota.c:68)
   nft_do_chain_inet
   nf_hook_slow
   __ip_local_out
   ip_push_pending_frames
   udp_send_skb
   udp_sendmsg
   __x64_sys_sendto

  Allocated by task 77:
   __alloc_skb (net/core/skbuff.c:704)
   __nft_obj_notify (include/net/netlink.h:1055
                     net/netfilter/nf_tables_api.c:8731)
   nft_quota_obj_eval (net/netfilter/nft_quota.c:68)
   nft_do_chain

  Freed by task 79:
   nf_tables_commit (include/linux/skbuff.h:1332
                     net/netfilter/nf_tables_api.c:10759
                     net/netfilter/nf_tables_api.c:11185)
   nfnetlink_rcv_batch (net/netfilter/nfnetlink.c:574)
   netlink_unicast
   netlink_sendmsg

  The buggy address belongs to the cache skbuff_head_cache of size 232

Queueing from the packet path is wrong even leaving the race aside:
notify_list is only drained by nft_commit_notify() from nf_tables_commit() (:11185), so a notification enqueued outside a transaction is not sent until some later netlink batch commits, if one ever does.

The gfp argument that nft_obj_notify() still takes is a leftover of the pre-67cc570edaa0 behaviour, where this path called nfnetlink_send() directly. Restore that: split the message construction out into nft_obj_notify_alloc() and let each caller decide what to do with the skb. nft_obj_notify(), the exported one reached from the packet path, sends it straight away; nf_tables_obj_notify(), which runs under commit_mutex, keeps queueing it, so transaction notifications are still coalesced.

---
 net/netfilter/nf_tables_api.c | 36 ++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

index 67b830b45cc4b..608ef18585367 100644
@@ -7808,18 +7808,17 @@ static int nf_tables_delobj(struct sk_buff *skb, const struct nfnl_info *info,
 	return nft_delobj(&ctx, obj);
 }
 
-static void
-__nft_obj_notify(struct net *net, const struct nft_table *table,
-		 struct nft_object *obj, u32 portid, u32 seq, int event,
-		 u16 flags, int family, int report, gfp_t gfp)
+static struct sk_buff *
+nft_obj_notify_alloc(struct net *net, const struct nft_table *table,
+		     struct nft_object *obj, u32 portid, u32 seq, int event,
+		     u16 flags, int family, int report, gfp_t gfp)
 {
-	struct nftables_pernet *nft_net = nft_pernet(net);
 	struct sk_buff *skb;
 	int err;
 
 	if (!report &&
 	    !nfnetlink_has_listeners(net, NFNLGRP_NFTABLES))
-		return;
+		return NULL;
 
 	skb = nlmsg_new(NLMSG_GOODSIZE, gfp);
 	if (skb == NULL)

@@ -7833,10 +7832,10 @@ __nft_obj_notify(struct net *net, const struct nft_table *table,
 		goto err;
 	}
 
-	nft_notify_enqueue(skb, report, &nft_net->notify_list);
-	return;
+	return skb;
 err:
 	nfnetlink_set_err(net, portid, NFNLGRP_NFTABLES, -ENOBUFS);
+	return NULL;
 }
 
 void nft_obj_notify(struct net *net, const struct nft_table *table,

@@ -7845,6 +7844,7 @@ void nft_obj_notify(struct net *net, const struct nft_table *table,
 {
 	char *buf = kasprintf(gfp, "%s:%u",
 			      table->name, nft_base_seq(net));
+	struct sk_buff *skb;
 
 	audit_log_nfcfg(buf,
 			family,

@@ -7855,17 +7855,27 @@ void nft_obj_notify(struct net *net, const struct nft_table *table,
 			gfp);
 	kfree(buf);
 
-	__nft_obj_notify(net, table, obj, portid, seq, event,
-			 flags, family, report, gfp);
+	/* Called from the packet path, holding no mutex: notify_list is
+	 * serialised by commit_mutex, so send this notification directly.
+	 */
+	skb = nft_obj_notify_alloc(net, table, obj, portid, seq, event,
+				   flags, family, report, gfp);
+	if (skb)
+		nfnetlink_send(skb, net, portid, NFNLGRP_NFTABLES, report, gfp);
 }
 EXPORT_SYMBOL_GPL(nft_obj_notify);
 
 static void nf_tables_obj_notify(const struct nft_ctx *ctx,
 				 struct nft_object *obj, int event)
 {
-	__nft_obj_notify(ctx->net, ctx->table, obj, ctx->portid,
-			 ctx->seq, event, ctx->flags, ctx->family,
-			 ctx->report, GFP_KERNEL);
+	struct nftables_pernet *nft_net = nft_pernet(ctx->net);
+	struct sk_buff *skb;
+
+	skb = nft_obj_notify_alloc(ctx->net, ctx->table, obj, ctx->portid,
+				   ctx->seq, event, ctx->flags, ctx->family,
+				   ctx->report, GFP_KERNEL);
+	if (skb)
+		nft_notify_enqueue(skb, ctx->report, &nft_net->notify_list);
 }
 
 /*

2.53.0