[PATCH net 1/5] rxrpc: input: reject ACKALL outside transmit phase

[David Howells]

From: Wyatt Feng <bronzed_45_vested at icloud.com>

rxrpc_input_ackall() accepts ACKALL packets without checking whether
the call is in a state that can legitimately have outstanding transmit
buffers.  A forged ACKALL can therefore reach a new service call in
RXRPC_CALL_SERVER_RECV_REQUEST before any reply packets have been
queued.

In that state call->tx_top is zero and call->tx_queue is NULL, so
rxrpc_rotate_tx_window() dereferences a NULL txqueue and triggers a
null-pointer dereference.

Fix rxrpc_input_ackall() to mirror the transmit-state gating already
used for normal ACK processing, and ignore ACKALL when there is no
outstanding transmit window to rotate.

Fixes: b341a0263b1b ("rxrpc: Implement progressive transmission queue struct")
Cc: stable at vger.kernel.org
Reported-by: Yuan Tan <yuantan098 at gmail.com>
Reported-by: Yifan Wu <yifanwucs at gmail.com>
Reported-by: Juefei Pu <tomapufckgml at gmail.com>
Reported-by: Zhengchuan Liang <zcliangcn at gmail.com>
Reported-by: Xin Liu <bird at lzu.edu.cn>
Assisted-by: Codex:GPT-5.4
Signed-off-by: Wyatt Feng <bronzed_45_vested at icloud.com>
Signed-off-by: Ren Wei <n05ec at lzu.edu.cn>
Signed-off-by: David Howells <dhowells at redhat.com>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: linux-afs at lists.infradead.org
---
 net/rxrpc/input.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index ce761466b02d..37881dffa898 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -1214,8 +1214,22 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 static void rxrpc_input_ackall(struct rxrpc_call *call, struct sk_buff *skb)
 {
 	struct rxrpc_ack_summary summary = { 0 };
+	rxrpc_seq_t top = READ_ONCE(call->tx_top);
+
+	switch (__rxrpc_call_state(call)) {
+	case RXRPC_CALL_CLIENT_SEND_REQUEST:
+	case RXRPC_CALL_CLIENT_AWAIT_REPLY:
+	case RXRPC_CALL_SERVER_SEND_REPLY:
+	case RXRPC_CALL_SERVER_AWAIT_ACK:
+		break;
+	default:
+		return;
+	}
+
+	if (call->tx_bottom == top)
+		return;
 
-	if (rxrpc_rotate_tx_window(call, call->tx_top, &summary))
+	if (rxrpc_rotate_tx_window(call, top, &summary))
 		rxrpc_end_tx_phase(call, false, rxrpc_eproto_unexpected_ackall);
 }