FAILED: patch "[PATCH] X.509: Fix validation of ASN.1 certificate header" failed to apply to 5.10-stable tree

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 <[email protected]>.

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 3b626ba431c4501512ad07549310685e07fe4706
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026071443-shed-dipper-bf70@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 3b626ba431c4501512ad07549310685e07fe4706 Mon Sep 17 00:00:00 2001
From: Lukas Wunner <[email protected]>
Date: Thu, 14 May 2026 08:55:58 +0200
Subject: [PATCH] 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.

index a41741326998..0d516c77cc26 100644
@@ -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];

From: Lukas Wunner <[email protected]>

[ Upstream commit 3b626ba431c4501512ad07549310685e07fe4706 ]

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.

---
 certs/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 16a220887a53e8..c7bcf3f6a77e39 100644
@@ -20,7 +20,7 @@ int 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];

2.53.0