FAILED: patch "[PATCH] rxrpc: reject undecryptable rxkad response tickets" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x fe4447cd95623b1cfacc15f280aab73a6d7340b2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026041318-resource-luckless-1cf9@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From fe4447cd95623b1cfacc15f280aab73a6d7340b2 Mon Sep 17 00:00:00 2001
From: Yuqi Xu <[email protected]>
Date: Wed, 8 Apr 2026 13:12:39 +0100
Subject: [PATCH] rxrpc: reject undecryptable rxkad response tickets

rxkad_decrypt_ticket() decrypts the RXKAD response ticket and then parses the buffer as plaintext without checking whether crypto_skcipher_decrypt() succeeded.

A malformed RESPONSE can therefore use a non-block-aligned ticket length, make the decrypt operation fail, and still drive the ticket parser with attacker-controlled bytes.

Check the decrypt result and abort the connection with RXKADBADTICKET when ticket decryption fails.

index e923d6829008..0f79d694cb08 100644
@@ -958,6 +958,7 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
 	struct in_addr addr;
 	unsigned int life;
 	time64_t issue, now;
+	int ret;
 	bool little_endian;
 	u8 *p, *q, *name, *end;
 

@@ -977,8 +978,11 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
 	sg_init_one(&sg[0], ticket, ticket_len);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
 	skcipher_request_set_crypt(req, sg, sg, ticket_len, iv.x);
-	crypto_skcipher_decrypt(req);
+	ret = crypto_skcipher_decrypt(req);
 	skcipher_request_free(req);
+	if (ret < 0)
+		return rxrpc_abort_conn(conn, skb, RXKADBADTICKET, -EPROTO,
+					rxkad_abort_resp_tkt_short);
 
 	p = ticket;
 	end = p + ticket_len;

From: Yuqi Xu <[email protected]>

[ Upstream commit fe4447cd95623b1cfacc15f280aab73a6d7340b2 ]

rxkad_decrypt_ticket() decrypts the RXKAD response ticket and then parses the buffer as plaintext without checking whether crypto_skcipher_decrypt() succeeded.

A malformed RESPONSE can therefore use a non-block-aligned ticket length, make the decrypt operation fail, and still drive the ticket parser with attacker-controlled bytes.

Check the decrypt result and abort the connection with RXKADBADTICKET when ticket decryption fails.

---
 net/rxrpc/rxkad.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

index 78fa0524156f1..84a61fa18bc06 100644
@@ -1013,8 +1013,13 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
 	sg_init_one(&sg[0], ticket, ticket_len);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
 	skcipher_request_set_crypt(req, sg, sg, ticket_len, iv.x);
-	crypto_skcipher_decrypt(req);
+	ret = crypto_skcipher_decrypt(req);
 	skcipher_request_free(req);
+	if (ret < 0) {
+		abort_code = RXKADBADTICKET;
+		ret = -EPROTO;
+		goto other_error;
+	}
 
 	p = ticket;
 	end = p + ticket_len;

2.53.0