Patch "rxrpc: Fix missing validation of ticket length in non-XDR key preparsing" has been added to the 6.12-stable tree

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

    rxrpc: Fix missing validation of ticket length in non-XDR key preparsing

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rxrpc-fix-missing-validation-of-ticket-length-in-non-xdr-key-preparsing.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From ac33733b10b484d666f97688561670afd5861383 Mon Sep 17 00:00:00 2001
From: Anderson Nascimento <anderson at allelesecurity.com>
Date: Wed, 22 Apr 2026 17:14:35 +0100
Subject: rxrpc: Fix missing validation of ticket length in non-XDR key preparsing

From: Anderson Nascimento <anderson at allelesecurity.com>

commit ac33733b10b484d666f97688561670afd5861383 upstream.

In rxrpc_preparse(), there are two paths for parsing key payloads: the
XDR path (for large payloads) and the non-XDR path (for payloads <= 28
bytes). While the XDR path (rxrpc_preparse_xdr_rxkad()) correctly
validates the ticket length against AFSTOKEN_RK_TIX_MAX, the non-XDR
path fails to do so.

This allows an unprivileged user to provide a very large ticket length.
When this key is later read via rxrpc_read(), the total
token size (toksize) calculation results in a value that exceeds
AFSTOKEN_LENGTH_MAX, triggering a WARN_ON().

[ 2001.302904] WARNING: CPU: 2 PID: 2108 at net/rxrpc/key.c:778 rxrpc_read+0x109/0x5c0 [rxrpc]

Fix this by adding a check in the non-XDR parsing path of rxrpc_preparse()
to ensure the ticket length does not exceed AFSTOKEN_RK_TIX_MAX,
bringing it into parity with the XDR parsing logic.

Fixes: 8a7a3eb4ddbe ("KEYS: RxRPC: Use key preparsing")
Fixes: 84924aac08a4 ("rxrpc: Fix checker warning")
Reported-by: Anderson Nascimento <anderson at allelesecurity.com>
Signed-off-by: Anderson Nascimento <anderson at allelesecurity.com>
Signed-off-by: David Howells <dhowells at redhat.com>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: Jeffrey Altman <jaltman at auristor.com>
cc: Simon Horman <horms at kernel.org>
cc: linux-afs at lists.infradead.org
cc: stable at kernel.org
Link: https://patch.msgid.link/20260422161438.2593376-7-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 net/rxrpc/key.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/rxrpc/key.c
+++ b/net/rxrpc/key.c
@@ -340,6 +340,10 @@ static int rxrpc_preparse(struct key_pre
 	if (v1->security_index != RXRPC_SECURITY_RXKAD)
 		goto error;
 
+	ret = -EKEYREJECTED;
+	if (v1->ticket_length > AFSTOKEN_RK_TIX_MAX)
+		goto error;
+
 	plen = sizeof(*token->kad) + v1->ticket_length;
 	prep->quotalen += plen + sizeof(*token);
 


Patches currently in stable-queue which might be from anderson at allelesecurity.com are

queue-6.12/rxrpc-fix-missing-validation-of-ticket-length-in-non-xdr-key-preparsing.patch