FAILED: patch "[PATCH] ip: orphan prefetched skbs before multicast forwarding" failed to apply to 5.10-stable tree

PATCH New [email protected] 2 participants 4 messages Sep 3 – Sep 8

Subsystems (3)

Networking Stable branch IPv4/IPv6

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lore

[email protected]

author maintainer

2026-09-03 14:24 UTC #0 lore raw

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x e36ce6e78fe3fc3c071a26750783b7ba081ce10d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090320-tiptop-scrooge-9ea0@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From e36ce6e78fe3fc3c071a26750783b7ba081ce10d Mon Sep 17 00:00:00 2001
From: Zhiling Zou <[email protected]>
Date: Thu, 13 Aug 2026 00:36:38 +0800
Subject: [PATCH] ip: orphan prefetched skbs before multicast forwarding

IPv4 and IPv6 input preserve an skb->sk association installed by bpf_sk_assign() so that local delivery can use the selected socket under RCU. Both address families can also prefetch a socket in UDP early demux. In both paths (BPF and UDP early demux) a reference is not guaranteed to be held on the socket.

When a multicast packet is not locally deliverable, IPv6 hands the original skb to ip6_mr_input(). IPv4's ip_mr_input() similarly keeps the original skb when local delivery is not needed. Either path can put the skb on an unresolved multicast route queue or forward it after the receive-side RCU section ends.

After the prefetched socket is destroyed, a later skb free invokes sock_pfree() and dereferences the stale skb->sk. Orphan the skb before each non-local multicast forwarding path. Local delivery retains the original skb; the existing skb_clone() calls provide multicast forwarding with a socket-free clone.

Fixes cf7fbe660f2d ("bpf: Add socket assign support")

Fixes 08842c43d016 ("udp: no longer touch sk->sk_refcnt in early demux")

Cc [email protected]

Reported-by Vega <[email protected]>

Signed-off-by Zhiling Zou <[email protected]>

Reported-by Vega <[email protected]>

Signed-off-by Zhiling Zou <[email protected]>

Reviewed-by Ido Schimmel <[email protected]>

Link https://patch.msgid.link/0c52eb3d7532aaf8bccf37e0f7c922143c639735.1786552223.git.zhilinz@nebusec.ai open here

Signed-off-by Paolo Abeni <[email protected]>

net/ipv4/ipmr.c +3 -0

index 1d9a4ac14fce..e5f2b1c6150d 100644
@@ -2213,6 +2213,9 @@ int ip_mr_input(struct sk_buff *skb)
 	if (IPCB(skb)->flags & IPSKB_FORWARDED)
 		goto dont_forward;
 
+	if (!local)
+		skb_orphan(skb);
+
 	mrt = ipmr_rt_fib_lookup(net, skb);
 	if (IS_ERR(mrt)) {
 		kfree_skb(skb);

net/ipv6/ip6_input.c +1 -0

index 8972863c93ee..d332ec60f915 100644
@@ -622,6 +622,7 @@ int ip6_mc_input(struct sk_buff *skb)
 		if (deliver) {
 			skb2 = skb_clone(skb, GFP_ATOMIC);
 		} else {
+			skb_orphan(skb);
 			skb2 = skb;
 			skb = NULL;
 		}

Sasha Levin

maintainer

2026-09-08 23:02 UTC #1 lore raw

PATCH 1/3 inet: frags: add inet_frag_putn() helper

From: Eric Dumazet <[email protected]>

[ Upstream commit ae2d90355aa5592b0e99c8bbb4c3fa1d8e205f1b ]

inet_frag_putn() can release multiple references
in one step.

Use it in inet_frags_free_cb().

Replace inet_frag_put(X) with inet_frag_putn(X, 1)

Signed-off-by Eric Dumazet <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Paolo Abeni <[email protected]>

Stable-dep-of: e36ce6e78fe3 ("ip: orphan prefetched skbs before multicast forwarding")

Signed-off-by Sasha Levin <[email protected]>

---
 include/net/inet_frag.h                 | 4 ++--
 include/net/ipv6_frag.h                 | 3 ++-
 net/ieee802154/6lowpan/reassembly.c     | 7 ++++---
 net/ipv4/inet_fragment.c                | 3 +--
 net/ipv4/ip_fragment.c                  | 2 +-
 net/ipv6/netfilter/nf_conntrack_reasm.c | 3 ++-
 net/ipv6/reassembly.c                   | 4 ++--
 7 files changed, 14 insertions(+), 12 deletions(-)

include/net/inet_frag.h +2 -2

index 4cbd413e71a3f..1a212499fc98a 100644
@@ -135,9 +135,9 @@ struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key);
 /* Free all skbs in the queue; return the sum of their truesizes. */
 unsigned int inet_frag_rbtree_purge(struct rb_root *root);
 
-static inline void inet_frag_put(struct inet_frag_queue *q)
+static inline void inet_frag_putn(struct inet_frag_queue *q, int refs)
 {
-	if (refcount_dec_and_test(&q->refcnt))
+	if (refs && refcount_sub_and_test(refs, &q->refcnt))
 		inet_frag_destroy(q);
 }

include/net/ipv6_frag.h +2 -1

index 0a4779175a523..3443c7905b785 100644
@@ -65,6 +65,7 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
 {
 	struct net_device *dev = NULL;
 	struct sk_buff *head;
+	int refs = 1;
 
 	rcu_read_lock();
 	/* Paired with the WRITE_ONCE() in fqdir_pre_exit(). */

@@ -107,7 +108,7 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
 	spin_unlock(&fq->q.lock);
 out_rcu_unlock:
 	rcu_read_unlock();
-	inet_frag_put(&fq->q);
+	inet_frag_putn(&fq->q, refs);
 }
 
 /* Check if the upper layer header is truncated in the first fragment. */

net/ieee802154/6lowpan/reassembly.c +4 -3

index be6f06adefe0a..f5b554894d024 100644
@@ -45,6 +45,7 @@ static void lowpan_frag_expire(struct timer_list *t)
 {
 	struct inet_frag_queue *frag = from_timer(frag, t, timer);
 	struct frag_queue *fq;
+	int refs = 1;
 
 	fq = container_of(frag, struct frag_queue, q);

@@ -56,7 +57,7 @@ static void lowpan_frag_expire(struct timer_list *t)
 	inet_frag_kill(&fq->q);
 out:
 	spin_unlock(&fq->q.lock);
-	inet_frag_put(&fq->q);
+	inet_frag_putn(&fq->q, refs);
 }
 
 static inline struct lowpan_frag_queue *

@@ -301,13 +302,13 @@ int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
 
 	fq = fq_find(net, cb, &hdr.source, &hdr.dest);
 	if (fq != NULL) {
-		int ret;
+		int ret, refs = 1;
 
 		spin_lock(&fq->q.lock);
 		ret = lowpan_frag_queue(fq, skb, frag_type);
 		spin_unlock(&fq->q.lock);
 
-		inet_frag_put(&fq->q);
+		inet_frag_putn(&fq->q, refs);
 		return ret;
 	}

net/ipv4/inet_fragment.c +1 -2

index 18217537cb298..ef2ef64dc8af4 100644
@@ -144,8 +144,7 @@ static void inet_frags_free_cb(void *ptr, void *arg)
 	}
 	spin_unlock_bh(&fq->lock);
 
-	if (refcount_sub_and_test(count, &fq->refcnt))
-		inet_frag_destroy(fq);
+	inet_frag_putn(fq, count);
 }
 
 static void fqdir_work_fn(struct work_struct *work)

net/ipv4/ip_fragment.c +1 -1

index ec2264adf2a6a..f24e498dd1efc 100644
@@ -107,7 +107,7 @@ static void ip4_frag_free(struct inet_frag_queue *q)
 
 static void ipq_put(struct ipq *ipq)
 {
-	inet_frag_put(&ipq->q);
+	inet_frag_putn(&ipq->q, 1);
 }
 
 /* Kill ipq entry. It is not destroyed immediately,

net/ipv6/netfilter/nf_conntrack_reasm.c +2 -1

index 8313069b9f391..3d9bff1675323 100644
@@ -447,6 +447,7 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
 	struct frag_hdr *fhdr;
 	struct frag_queue *fq;
 	struct ipv6hdr *hdr;
+	int refs = 1;
 	u8 prevhdr;
 
 	/* Jumbo payload inhibits frag. header */

@@ -489,7 +490,7 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
 	}
 
 	spin_unlock_bh(&fq->q.lock);
-	inet_frag_put(&fq->q);
+	inet_frag_putn(&fq->q, refs);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);

net/ipv6/reassembly.c +2 -2

index 6993675171556..31bfc7932378a 100644
@@ -374,7 +374,7 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
 	fq = fq_find(net, fhdr->identification, hdr, iif);
 	if (fq) {
 		u32 prob_offset = 0;
-		int ret;
+		int ret, refs = 1;
 
 		spin_lock(&fq->q.lock);

@@ -383,7 +383,7 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
 				     &prob_offset);
 
 		spin_unlock(&fq->q.lock);
-		inet_frag_put(&fq->q);
+		inet_frag_putn(&fq->q, refs);
 		if (prob_offset) {
 			__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
 					IPSTATS_MIB_INHDRERRORS);

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-08 23:02 UTC #2 lore raw

PATCH 2/3 ipv4: frags: remove ipq_put()

From: Eric Dumazet <[email protected]>

[ Upstream commit a2fb987c0ecf0498cc17056339cb11d128c46ab7 ]

Replace ipq_put() with inet_frag_putn()

Signed-off-by Eric Dumazet <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Paolo Abeni <[email protected]>

For the stable backport, retain the existing ip_expire() error and skb freeing paths. Also brace the multicast delivery conditional so that the dependent fix can add its non-local skb orphaning without conflict.

Stable-dep-of: e36ce6e78fe3 ("ip: orphan prefetched skbs before multicast forwarding")

Signed-off-by Sasha Levin <[email protected]>

---
 net/ipv4/ip_fragment.c | 15 ++++-----------
 net/ipv6/ip6_input.c   |  4 ++--
 2 files changed, 6 insertions(+), 13 deletions(-)

net/ipv4/ip_fragment.c +4 ~~-11~~

index f24e498dd1efc..53186d06fb27a 100644
@@ -102,14 +102,6 @@ static void ip4_frag_free(struct inet_frag_queue *q)
 		inet_putpeer(qp->peer);
 }
 
-
-/* Destruction primitives. */
-
-static void ipq_put(struct ipq *ipq)
-{
-	inet_frag_putn(&ipq->q, 1);
-}
-
 /* Kill ipq entry. It is not destroyed immediately,
  * because caller (and someone more) holds reference count.
  */

@@ -138,6 +130,7 @@ static void ip_expire(struct timer_list *t)
 	struct net *net;
 	struct ipq *qp;
 	int err;
+	int refs = 1;
 
 	qp = container_of(frag, struct ipq, q);
 	net = qp->q.fqdir->net;

@@ -195,7 +188,7 @@ static void ip_expire(struct timer_list *t)
 out_rcu_unlock:
 	rcu_read_unlock();
 	kfree_skb(head);
-	ipq_put(qp);
+	inet_frag_putn(&qp->q, refs);
 }
 
 /* Find the correct entry in the "incomplete datagrams" queue for

@@ -484,14 +477,14 @@ int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
 	/* Lookup (or create) queue header */
 	qp = ip_find(net, ip_hdr(skb), user, vif);
 	if (qp) {
-		int ret;
+		int ret, refs = 1;
 
 		spin_lock(&qp->q.lock);
 
 		ret = ip_frag_queue(qp, skb);
 
 		spin_unlock(&qp->q.lock);
-		ipq_put(qp);
+		inet_frag_putn(&qp->q, refs);
 		return ret;
 	}

net/ipv6/ip6_input.c +2 -2

index 8cf5b10eee695..493666b0c6098 100644
@@ -554,9 +554,9 @@ int ip6_mc_input(struct sk_buff *skb)
 			/* unknown RA - process it normally */
 		}
 
-		if (deliver)
+		if (deliver) {
 			skb2 = skb_clone(skb, GFP_ATOMIC);
-		else {
+		} else {
 			skb2 = skb;
 			skb = NULL;
 		}

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-08 23:02 UTC #3 lore raw

PATCH 3/3 ip: orphan prefetched skbs before multicast forwarding

In reply to Sasha Levin

From: Zhiling Zou <[email protected]>

[ Upstream commit e36ce6e78fe3fc3c071a26750783b7ba081ce10d ]

Fixes cf7fbe660f2d ("bpf: Add socket assign support")

Fixes 08842c43d016 ("udp: no longer touch sk->sk_refcnt in early demux")

Cc [email protected]

Reported-by Vega <[email protected]>

Signed-off-by Zhiling Zou <[email protected]>

Reported-by Vega <[email protected]>

Signed-off-by Zhiling Zou <[email protected]>

Reviewed-by Ido Schimmel <[email protected]>

Link https://patch.msgid.link/0c52eb3d7532aaf8bccf37e0f7c922143c639735.1786552223.git.zhilinz@nebusec.ai open here

Signed-off-by Paolo Abeni <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 net/ipv4/ipmr.c      | 3 +++
 net/ipv6/ip6_input.c | 1 +
 2 files changed, 4 insertions(+)

net/ipv4/ipmr.c +3 -0

index 6e4f91e76e2d3..bd8d828818aac 100644
@@ -2112,6 +2112,9 @@ int ip_mr_input(struct sk_buff *skb)
 	if (IPCB(skb)->flags & IPSKB_FORWARDED)
 		goto dont_forward;
 
+	if (!local)
+		skb_orphan(skb);
+
 	mrt = ipmr_rt_fib_lookup(net, skb);
 	if (IS_ERR(mrt)) {
 		kfree_skb(skb);

net/ipv6/ip6_input.c +1 -0

index 493666b0c6098..db2f74f7ccd37 100644
@@ -557,6 +557,7 @@ int ip6_mc_input(struct sk_buff *skb)
 		if (deliver) {
 			skb2 = skb_clone(skb, GFP_ATOMIC);
 		} else {
+			skb_orphan(skb);
 			skb2 = skb;
 			skb = NULL;
 		}

Signature · 1 line

2.53.0