From: Oliver Hartkopp The skb extension ids range from 0 .. 7 to fit their bits as flags into a single byte. The ids are automatically enumnerated in enum skb_ext_id in skbuff.h, where SKB_EXT_NUM is defined as the last value. When having 8 skb extension ids (0 .. 7), SKB_EXT_NUM becomes 8 which is a valid value for SKB_EXT_NUM. This patch intentionally lacks a Fixes tag. Backporting is pointless as former kernels did not use the entire range of skb extension ids. Link: https://lore.kernel.org/netdev/aXoMqaA7b2CqJZNA@strlen.de/ Reviewed-by: Florian Westphal Signed-off-by: Oliver Hartkopp --- net/core/skbuff.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 648c20e19038..609851d70173 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5156,11 +5156,11 @@ static __always_inline unsigned int skb_ext_total_length(void) return l; } static void skb_extensions_init(void) { - BUILD_BUG_ON(SKB_EXT_NUM >= 8); + BUILD_BUG_ON(SKB_EXT_NUM > 8); #if !IS_ENABLED(CONFIG_KCOV_INSTRUMENT_ALL) BUILD_BUG_ON(skb_ext_total_length() > 255); #endif skbuff_ext_cache = kmem_cache_create("skbuff_ext_cache", --- base-commit: 021718d2cc1a2df2f53b06968fa89280199371bd change-id: 20260205-skb_ext-a04c61cc985e Best regards, -- Oliver Hartkopp