On Mon, 18 Aug 2025 13:27:24 -0700
Eric Biggers <ebiggers@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
>
> v2: sent as standalone patch targeting net instead of net-next.
>
> net/ipv6/seg6_hmac.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
The fix looks good to me. Thanks!
Ciao,
Andrea
Reviewed-by: Andrea Mayer <andrea.mayer@xxxxxxxxxxx>
> 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);
>
> base-commit: 715c7a36d59f54162a26fac1d1ed8dc087a24cf1
> --
> 2.50.1
>
