On Fri, 15 Aug 2025 20:11:34 -0700 Eric Biggers ebiggers@kernel.org wrote:

To prevent timing attacks, MACs need to be compared in constant time. Use the appropriate helper function for this.

Fixes: bf355b8d2c30 ("ipv6: sr: add core files for SR HMAC support") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers ebiggers@kernel.org

---

net/ipv6/seg6_hmac.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

Hi Eric,

Thanks for the fix!

I believe it would be best to submit this fix separately from the current patch set. Since this addresses a bug rather than an enhancement or cleanup, sending it individually with the 'net' tag will help facilitate applying this patch to the net tree.

Ciao, Andrea

diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c index f78ecb6ad8383..5dae892bbc73b 100644 --- a/net/ipv6/seg6_hmac.c +++ b/net/ipv6/seg6_hmac.c @@ -33,10 +33,11 @@ #include <net/ip6_route.h> #include <net/addrconf.h> #include <net/xfrm.h> #include <crypto/hash.h> +#include <crypto/utils.h> #include <net/seg6.h> #include <net/genetlink.h> #include <net/seg6_hmac.h> #include <linux/random.h> @@ -278,11 +279,11 @@ bool seg6_hmac_validate_skb(struct sk_buff *skb) return false; if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output)) return false;

• if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)

• if (crypto_memneq(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN)) return false;

return true; } EXPORT_SYMBOL(seg6_hmac_validate_skb); -- 2.50.1