The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x a458b2902115b26a25d67393b12ddd57d1216aaa # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025082249-consumer-mortician-8ee1@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a458b2902115b26a25d67393b12ddd57d1216aaa Mon Sep 17 00:00:00 2001 From: Eric Biggers ebiggers@kernel.org Date: Mon, 18 Aug 2025 13:27:24 -0700 Subject: [PATCH] ipv6: sr: Fix MAC comparison to be constant-time

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 Reviewed-by: Andrea Mayer andrea.mayer@uniroma2.it Link: https://patch.msgid.link/20250818202724.15713-1-ebiggers@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org

diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c index d77b52523b6a..fd58426f222b 100644 --- a/net/ipv6/seg6_hmac.c +++ b/net/ipv6/seg6_hmac.c @@ -35,6 +35,7 @@ #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> @@ -280,7 +281,7 @@ bool seg6_hmac_validate_skb(struct sk_buff *skb) 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;