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net: Make skb_ext_put_mctp() idempotent

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The MCTP flow extension can be released either when it is deleted from an
skb or when the last skb holding the extension block is freed. Handle the
release in __skb_ext_del(), which is currently missing, and make
skb_ext_put_mctp() safe to call from both paths.

This will let __skb_ext_put() release the MCTP key without checking whether
the extension is present first, which is needed if we want to reuse skb_ext
chunks area after skb scrubbing.

Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20260831-skb-ext-prep-work-v1-2-ecc2a8542fd9@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Sitnicki 2026-08-31 08:27:39 +02:00 committed by Jakub Kicinski
parent d7470cba6d
commit dbe45b209e
1 changed files with 16 additions and 6 deletions
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22
net/core/skbuff.c
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@ -7248,8 +7248,11 @@ static void skb_ext_put_sp(struct sec_path *sp)
#ifdef CONFIG_MCTP_FLOWS
static void skb_ext_put_mctp(struct mctp_flow *flow)
{
if (flow->key)
mctp_key_unref(flow->key);
if (!flow->key)
return;
mctp_key_unref(flow->key);
flow->key = NULL;
}
#endif
@ -7261,13 +7264,20 @@ void __skb_ext_del(struct sk_buff *skb, enum skb_ext_id id)
if (skb->active_extensions == 0) {
skb->extensions = NULL;
__skb_ext_put(ext);
#ifdef CONFIG_XFRM
} else if (id == SKB_EXT_SEC_PATH &&
refcount_read(&ext->refcnt) == 1) {
return;
}
if (refcount_read(&ext->refcnt) > 1)
return;
#ifdef CONFIG_XFRM
if (id == SKB_EXT_SEC_PATH)
skb_ext_put_sp(skb_ext_get_ptr(ext, SKB_EXT_SEC_PATH));
#endif
}
#ifdef CONFIG_MCTP_FLOWS
if (id == SKB_EXT_MCTP)
skb_ext_put_mctp(skb_ext_get_ptr(ext, SKB_EXT_MCTP));
#endif
}
EXPORT_SYMBOL(__skb_ext_del);