Patch "rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial" has been added to the 6.18-stable tree

[gregkh at linuxfoundation.org]

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

    rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial

to the 6.18-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-use-of-wrong-skb-when-comparing-queued-resp-challenge-serial.patch
and it can be found in the queue-6.18 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 b33f5741bb187db8ff32e8f5b96def77cc94dfca Mon Sep 17 00:00:00 2001
From: Alok Tiwari <alok.a.tiwari at oracle.com>
Date: Wed, 8 Apr 2026 13:12:34 +0100
Subject: rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial

From: Alok Tiwari <alok.a.tiwari at oracle.com>

commit b33f5741bb187db8ff32e8f5b96def77cc94dfca upstream.

In rxrpc_post_response(), the code should be comparing the challenge serial
number from the cached response before deciding to switch to a newer
response, but looks at the newer packet private data instead, rendering the
comparison always false.

Fix this by switching to look at the older packet.

Fix further[1] to substitute the new packet in place of the old one if
newer and also to release whichever we don't use.

Fixes: 5800b1cf3fd8 ("rxrpc: Allow CHALLENGEs to the passed to the app for a RESPONSE")
Signed-off-by: Alok Tiwari <alok.a.tiwari at oracle.com>
Signed-off-by: David Howells <dhowells at redhat.com>
Reviewed-by: Jeffrey Altman <jaltman at auristor.com>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: Simon Horman <horms at kernel.org>
cc: linux-afs at lists.infradead.org
cc: stable at kernel.org
Link: https://sashiko.dev/#/patchset/20260319150150.4189381-1-dhowells%40redhat.com [1]
Link: https://patch.msgid.link/20260408121252.2249051-7-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 include/trace/events/rxrpc.h | 1 +
 net/rxrpc/conn_event.c       | 5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index a826cd80007b..f7f559204b87 100644
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -185,6 +185,7 @@
 	EM(rxrpc_skb_put_input,			"PUT input    ") \
 	EM(rxrpc_skb_put_jumbo_subpacket,	"PUT jumbo-sub") \
 	EM(rxrpc_skb_put_oob,			"PUT oob      ") \
+	EM(rxrpc_skb_put_old_response,		"PUT old-resp ") \
 	EM(rxrpc_skb_put_purge,			"PUT purge    ") \
 	EM(rxrpc_skb_put_purge_oob,		"PUT purge-oob") \
 	EM(rxrpc_skb_put_response,		"PUT response ") \
diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index 98ad9b51ca2c..c50cbfc5a313 100644
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -557,11 +557,11 @@ void rxrpc_post_response(struct rxrpc_connection *conn, struct sk_buff *skb)
 	spin_lock_irq(&local->lock);
 	old = conn->tx_response;
 	if (old) {
-		struct rxrpc_skb_priv *osp = rxrpc_skb(skb);
+		struct rxrpc_skb_priv *osp = rxrpc_skb(old);
 
 		/* Always go with the response to the most recent challenge. */
 		if (after(sp->resp.challenge_serial, osp->resp.challenge_serial))
-			conn->tx_response = old;
+			conn->tx_response = skb;
 		else
 			old = skb;
 	} else {
@@ -569,4 +569,5 @@ void rxrpc_post_response(struct rxrpc_connection *conn, struct sk_buff *skb)
 	}
 	spin_unlock_irq(&local->lock);
 	rxrpc_poke_conn(conn, rxrpc_conn_get_poke_response);
+	rxrpc_free_skb(old, rxrpc_skb_put_old_response);
 }
-- 
2.53.0



Patches currently in stable-queue which might be from alok.a.tiwari at oracle.com are

queue-6.18/rxrpc-fix-use-of-wrong-skb-when-comparing-queued-resp-challenge-serial.patch
queue-6.18/rxrpc-fix-rack-timer-warning-to-report-unexpected-mode.patch