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net: skb: clean up dead code after skb_kfree_head() simplification

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Since commit 0f42e3f4fe ("net: skb: fix cross-cache free of
KFENCE-allocated skb head"), skb_kfree_head() always calls kfree()
and no longer uses end_offset to distinguish between skb_small_head_cache
and generic kmalloc caches.

Clean up the leftovers:

- Remove the unused end_offset parameter from skb_kfree_head() and
  update all callers.
- Remove the SKB_SMALL_HEAD_HEADROOM guard in __skb_unclone_keeptruesize()
  which was protecting the old skb_kfree_head() logic.
- Update the SKB_SMALL_HEAD_CACHE_SIZE comment to reflect that the
  non-power-of-2 sizing is no longer used for free-path disambiguation.

No functional change.

Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260410034736.297900-1-jiayuan.chen@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jiayuan Chen
2026-04-10 11:47:32 +08:00
committed by Jakub Kicinski
parent e530b484b7
commit 5758be283f
1 changed files with 9 additions and 24 deletions
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33
net/core/skbuff.c
View File

@@ -106,10 +106,9 @@ static struct kmem_cache *skbuff_ext_cache __ro_after_init;
#define SKB_SMALL_HEAD_SIZE SKB_HEAD_ALIGN(max(MAX_TCP_HEADER, \
GRO_MAX_HEAD_PAD))
/* We want SKB_SMALL_HEAD_CACHE_SIZE to not be a power of two.
* This should ensure that SKB_SMALL_HEAD_HEADROOM is a unique
* size, and we can differentiate heads from skb_small_head_cache
* vs system slabs by looking at their size (skb_end_offset()).
/* SKB_SMALL_HEAD_CACHE_SIZE is the size used for the skbuff_small_head
* kmem_cache. The non-power-of-2 padding is kept for historical reasons and
* to avoid potential collisions with generic kmalloc bucket sizes.
*/
#define SKB_SMALL_HEAD_CACHE_SIZE \
(is_power_of_2(SKB_SMALL_HEAD_SIZE) ? \
@@ -1071,7 +1070,7 @@ static int skb_pp_frag_ref(struct sk_buff *skb)
return 0;
}
static void skb_kfree_head(void *head, unsigned int end_offset)
static void skb_kfree_head(void *head)
{
kfree(head);
}
@@ -1085,7 +1084,7 @@ static void skb_free_head(struct sk_buff *skb)
return;
skb_free_frag(head);
} else {
skb_kfree_head(head, skb_end_offset(skb));
skb_kfree_head(head);
}
}
@@ -2361,7 +2360,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
return 0;
nofrags:
skb_kfree_head(data, size);
skb_kfree_head(data);
nodata:
return -ENOMEM;
}
@@ -2407,20 +2406,6 @@ int __skb_unclone_keeptruesize(struct sk_buff *skb, gfp_t pri)
if (likely(skb_end_offset(skb) == saved_end_offset))
return 0;
/* We can not change skb->end if the original or new value
* is SKB_SMALL_HEAD_HEADROOM, as it might break skb_kfree_head().
*/
if (saved_end_offset == SKB_SMALL_HEAD_HEADROOM ||
skb_end_offset(skb) == SKB_SMALL_HEAD_HEADROOM) {
/* We think this path should not be taken.
* Add a temporary trace to warn us just in case.
*/
pr_err_once("__skb_unclone_keeptruesize() skb_end_offset() %u -> %u\n",
saved_end_offset, skb_end_offset(skb));
WARN_ON_ONCE(1);
return 0;
}
shinfo = skb_shinfo(skb);
/* We are about to change back skb->end,
@@ -6815,7 +6800,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
if (skb_cloned(skb)) {
/* drop the old head gracefully */
if (skb_orphan_frags(skb, gfp_mask)) {
skb_kfree_head(data, size);
skb_kfree_head(data);
return -ENOMEM;
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
@@ -6922,7 +6907,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
memcpy((struct skb_shared_info *)(data + size),
skb_shinfo(skb), offsetof(struct skb_shared_info, frags[0]));
if (skb_orphan_frags(skb, gfp_mask)) {
skb_kfree_head(data, size);
skb_kfree_head(data);
return -ENOMEM;
}
shinfo = (struct skb_shared_info *)(data + size);
@@ -6958,7 +6943,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
/* skb_frag_unref() is not needed here as shinfo->nr_frags = 0. */
if (skb_has_frag_list(skb))
kfree_skb_list(skb_shinfo(skb)->frag_list);
skb_kfree_head(data, size);
skb_kfree_head(data);
return -ENOMEM;
}
skb_release_data(skb, SKB_CONSUMED);