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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, David Howells <dhowells@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.5 360/367] rxrpc: Fix service call disconnection
Date:   Mon, 10 Feb 2020 04:34:33 -0800
Message-Id: <20200210122455.612514463@linuxfoundation.org>
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From: David Howells <dhowells@redhat.com>

[ Upstream commit b39a934ec72fa2b5a74123891f25273a38378b90 ]

The recent patch that substituted a flag on an rxrpc_call for the
connection pointer being NULL as an indication that a call was disconnected
puts the set_bit in the wrong place for service calls.  This is only a
problem if a call is implicitly terminated by a new call coming in on the
same connection channel instead of a terminating ACK packet.

In such a case, rxrpc_input_implicit_end_call() calls
__rxrpc_disconnect_call(), which is now (incorrectly) setting the
disconnection bit, meaning that when rxrpc_release_call() is later called,
it doesn't call rxrpc_disconnect_call() and so the call isn't removed from
the peer's error distribution list and the list gets corrupted.

KASAN finds the issue as an access after release on a call, but the
position at which it occurs is confusing as it appears to be related to a
different call (the call site is where the latter call is being removed
from the error distribution list and either the next or pprev pointer
points to a previously released call).

Fix this by moving the setting of the flag from __rxrpc_disconnect_call()
to rxrpc_disconnect_call() in the same place that the connection pointer
was being cleared.

Fixes: 5273a191dca6 ("rxrpc: Fix NULL pointer deref due to call->conn being cleared on disconnect")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/rxrpc/conn_object.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
index c0b3154f7a7e1..19e141eeed17d 100644
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -171,8 +171,6 @@ void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
 
 	_enter("%d,%x", conn->debug_id, call->cid);
 
-	set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
-
 	if (rcu_access_pointer(chan->call) == call) {
 		/* Save the result of the call so that we can repeat it if necessary
 		 * through the channel, whilst disposing of the actual call record.
@@ -225,6 +223,7 @@ void rxrpc_disconnect_call(struct rxrpc_call *call)
 	__rxrpc_disconnect_call(conn, call);
 	spin_unlock(&conn->channel_lock);
 
+	set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
 	conn->idle_timestamp = jiffies;
 }
 
-- 
2.20.1