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rds: Incorrect reference counting in TCP socket creation

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Commit 0933a578cd ("rds: tcp: use sock_create_lite() to create the
accept socket") has a reference counting issue in TCP socket creation
when accepting a new connection.  The code uses sock_create_lite() to
create a kernel socket.  But it does not do __module_get() on the
socket owner.  When the connection is shutdown and sock_release() is
called to free the socket, the owner's reference count is decremented
and becomes incorrect.  Note that this bug only shows up when the socket
owner is configured as a kernel module.

v2: Update comments

Fixes: 0933a578cd ("rds: tcp: use sock_create_lite() to create the accept socket")
Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Acked-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ka-Cheong Poon 2018-03-01 21:07:18 -08:00 committed by David S. Miller
parent a5f7b0eeb2
commit 84eef2b218
1 changed files with 11 additions and 3 deletions
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14
net/rds/tcp_listen.c
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2006 Oracle. All rights reserved.
* Copyright (c) 2006, 2018 Oracle. All rights reserved.
*
* This software is available to you under a choice of one of two
* licenses. You may choose to be licensed under the terms of the GNU
@ -142,12 +142,20 @@ int rds_tcp_accept_one(struct socket *sock)
if (ret)
goto out;
new_sock->type = sock->type;
new_sock->ops = sock->ops;
ret = sock->ops->accept(sock, new_sock, O_NONBLOCK, true);
if (ret < 0)
goto out;
/* sock_create_lite() does not get a hold on the owner module so we
* need to do it here. Note that sock_release() uses sock->ops to
* determine if it needs to decrement the reference count. So set
* sock->ops after calling accept() in case that fails. And there's
* no need to do try_module_get() as the listener should have a hold
* already.
*/
new_sock->ops = sock->ops;
__module_get(new_sock->ops->owner);
ret = rds_tcp_keepalive(new_sock);
if (ret < 0)
goto out;