ipv6: sr: Fix MAC comparison to be constant-time

commit a458b2902115b26a25d67393b12ddd57d1216aaa upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c
index bbf5b84a70fcabe0d380814aa4d99b95006925b8..e955008e732bf58208a9274218993628cf6fb3ee 100644 (file)
--- 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>
@@ -271,7 +272,7 @@ 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;