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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Baptiste Lepers <baptiste.lepers@gmail.com>,
        David Howells <dhowells@redhat.com>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 4.19 13/22] rxrpc: Call state should be read with READ_ONCE() under some circumstances
Date:   Fri, 22 Jan 2021 15:12:31 +0100
Message-Id: <20210122135732.441893605@linuxfoundation.org>
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From: Baptiste Lepers <baptiste.lepers@gmail.com>

[ Upstream commit a95d25dd7b94a5ba18246da09b4218f132fed60e ]

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.

Fixes: a158bdd3247b ("rxrpc: Fix call timeouts")
Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/161046715522.2450566.488819910256264150.stgit@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/rxrpc/input.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -446,7 +446,7 @@ static void rxrpc_input_data(struct rxrp
 	if (state >= RXRPC_CALL_COMPLETE)
 		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;