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authorKa-Cheong Poon <ka-cheong.poon@oracle.com>2018-03-01 21:07:18 -0800
committerDavid S. Miller <davem@davemloft.net>2018-03-02 09:40:27 -0500
commit84eef2b2187ed73c0e4520cbfeb874e964a0b56a (patch)
tree910036b61425b56e91761802c77dc2ea15357b2a /net
parenta5f7b0eeb219620e1f7388db817e2fb584c00b64 (diff)
rds: Incorrect reference counting in TCP socket creation
Commit 0933a578cd55 ("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: 0933a578cd55 ("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>
Diffstat (limited to 'net')
-rw-r--r--net/rds/tcp_listen.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index c061d6eb465d..22571189f21e 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -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;