git: 36ed9a84d17b - stable/15 - LinuxKPI: skbuff: add reference counting to the skb

The branch stable/15 has been updated by bz:

URL: https://cgit.FreeBSD.org/src/commit/?id=36ed9a84d17b58b83612bb4ec32bddfc56f991b2

commit 36ed9a84d17b58b83612bb4ec32bddfc56f991b2
Author:     Bjoern A. Zeeb <[email protected]>
AuthorDate: 2026-02-03 22:13:24 +0000
Commit:     Bjoern A. Zeeb <[email protected]>
CommitDate: 2026-07-26 16:48:25 +0000

    LinuxKPI: skbuff: add reference counting to the skb
    
    Sponsored by:   The FreeBSD Foundation
    
    (cherry picked from commit cb13e826ec45e11e964e1921d281e0a06ca5e152)
---
 sys/compat/linuxkpi/common/src/linux_skbuff.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/sys/compat/linuxkpi/common/src/linux_skbuff.c b/sys/compat/linuxkpi/common/src/linux_skbuff.c
index 5af9633691a6..d57c277c3267 100644
--- a/sys/compat/linuxkpi/common/src/linux_skbuff.c
+++ b/sys/compat/linuxkpi/common/src/linux_skbuff.c
@@ -140,6 +140,7 @@ linuxkpi_alloc_skb(size_t size, gfp_t gfp)
 	skb->head = skb->data = (uint8_t *)p;
 	skb_reset_tail_pointer(skb);
 	skb->end = skb->head + size;
+	refcount_set(&skb->refcnt, 1);
 
 	SKB_TRACE_FMT(skb, "data %p size %zu", (skb) ? skb->data : NULL, size);
 	return (skb);
@@ -180,6 +181,7 @@ linuxkpi_build_skb(void *data, size_t fragsz)
 	skb->head = skb->data = data;
 	skb_reset_tail_pointer(skb);
 	skb->end = skb->head + fragsz;
+	refcount_set(&skb->refcnt, 1);
 
 	return (skb);
 }
@@ -288,6 +290,20 @@ lkpi___skb_linearize(struct sk_buff *skb)
 	return (0);
 }
 
+static bool
+lkpi_skb_refcount_release(struct sk_buff *skb)
+{
+	if (skb == NULL)
+		return (false);
+
+	/* Do we need further tests to avoid freeing this one? */
+
+	if (!refcount_dec_and_test(&skb->refcnt))
+		return (false);
+
+	return (true);
+}
+
 void
 linuxkpi_kfree_skb(struct sk_buff *skb)
 {
@@ -298,6 +314,11 @@ linuxkpi_kfree_skb(struct sk_buff *skb)
 	if (skb == NULL)
 		return;
 
+	if (!lkpi_skb_refcount_release(skb)) {
+		SKB_TRACE_FMT(skb, "not freed due to refcnt");
+		return;
+	}
+
 	/*
 	 * XXX TODO this will go away once we have skb backed by mbuf.
 	 * currently we allow the mbuf to stay around and use a private