From: Lukas Wunner <lukas@wunner.de>
Date: Thu, 14 May 2026 06:55:58 +0000 (+0200)
Subject: X.509: Fix validation of ASN.1 certificate header
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3b626ba431c4501512ad07549310685e07fe4706;p=thirdparty%2Fkernel%2Flinux.git

X.509: Fix validation of ASN.1 certificate header

x509_load_certificate_list() seeks to enforce that a certificate starts
with 0x30 0x82 (ASN.1 SEQUENCE tag followed by a length of more than 256
and less than 65535 bytes).

But it only enforces that *either* of those two byte values are present,
instead of checking for the *conjunction* of the two values.  Fix it.

Fixes: 631cc66eb9ea ("MODSIGN: Provide module signing public keys to the kernel")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/r/20260508033917.B5873C2BCB0@smtp.kernel.org/
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v3.7+
Reviewed-by: Ignat Korchagin <ignat@linux.win>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

diff --git a/crypto/asymmetric_keys/x509_loader.c b/crypto/asymmetric_keys/x509_loader.c
index a417413269989..0d516c77cc26a 100644
--- a/crypto/asymmetric_keys/x509_loader.c
+++ b/crypto/asymmetric_keys/x509_loader.c
@@ -20,7 +20,7 @@ int x509_load_certificate_list(const u8 cert_list[],
 		 */
 		if (end - p < 4)
 			goto dodgy_cert;
-		if (p[0] != 0x30 &&
+		if (p[0] != 0x30 ||
 		    p[1] != 0x82)
 			goto dodgy_cert;
 		plen = (p[2] << 8) | p[3];