[PATCH 7.1 0028/2077] rxrpc: Fix rxrpc_rotate_tx_rotate() to check theres something to rotate

[Greg Kroah-Hartman]

7.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells at redhat.com>

commit a5462da5a349fc7f17ad5ebd899380260d03e7ed upstream.

Fix rxrpc_rotate_tx_rotate() to check that there's something in the
transmission buffer to be rotated before it attempts to rotate anything.

Fixes: b341a0263b1b ("rxrpc: Implement progressive transmission queue struct")
Link: https://sashiko.dev/#/patchset/20260618134802.2477777-1-dhowells%40redhat.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/20260624163819.3017002-12-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 net/rxrpc/input.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -236,6 +236,9 @@ static bool rxrpc_rotate_tx_window(struc
 		call->acks_lowest_nak = to;
 	}
 
+	if (after(seq, to))
+		return false;
+
 	/* We may have a left over fully-consumed buffer at the front that we
 	 * couldn't drop before (rotate_and_keep below).
 	 */