netdev - [PATCH net] rxrpc: Call state should be read with READ

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Message-ID: <161046715522.2450566.488819910256264150.stgit@warthog.procyon.org.uk>
Date:   Tue, 12 Jan 2021 15:59:15 +0000
From:   David Howells <dhowells@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Baptiste Lepers <baptiste.lepers@...il.com>,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
        dhowells@...hat.com
Subject: [PATCH net] rxrpc: Call state should be read with READ_ONCE() under
 some circumstances

From: Baptiste Lepers <baptiste.lepers@...il.com>

The call state may be changed at any time by the data-ready routine in
response to received packets, so if the call state is to be read and acted
upon several times in a function, READ_ONCE() must be used unless the call
state lock is held.

As it happens, we used READ_ONCE() to read the state a few lines above the
unmarked read in rxrpc_input_data(), so use that value rather than
re-reading it.

Signed-off-by: Baptiste Lepers <baptiste.lepers@...il.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 net/rxrpc/input.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 667c44aa5a63..dc201363f2c4 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -430,7 +430,7 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb)
 		return;
 	}
 
-	if (call->state == RXRPC_CALL_SERVER_RECV_REQUEST) {
+	if (state == RXRPC_CALL_SERVER_RECV_REQUEST) {
 		unsigned long timo = READ_ONCE(call->next_req_timo);
 		unsigned long now, expect_req_by;