[PATCH 3.18 006/183] geneve: Fix races between socket add and release.

Greg Kroah-Hartman
2015-01-25T19:02:29Z

From: Jesse Gross <jesse@nicira.com>

[ Upstream commit 12069401d895ff84076a50189ca842c0696b84b2 ]

Currently, searching for a socket to add a reference to is not
synchronized with deletion of sockets. This can result in use
after free if there is another operation that is removing a
socket at the same time. Solving this requires both holding the
appropriate lock and checking the refcount to ensure that it
has not already hit zero.

Inspired by a related (but not exactly the same) issue in the
VXLAN driver.

Fixes: 0b5e8b8e ("net: Add Geneve tunneling protocol driver")
CC: Andy Zhou <azhou@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/geneve.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

--- a/net/ipv4/geneve.c
+++ b/net/ipv4/geneve.c
@@ -302,6 +302,7 @@ struct geneve_sock *geneve_sock_add(stru
geneve_rcv_t *rcv, void *data,
bool no_share, bool ipv6)
{
+ struct geneve_net *gn = net_generic(net, geneve_net_id);
struct geneve_sock *gs;

gs = geneve_socket_create(net, port, rcv, data, ipv6);
@@ -311,15 +312,15 @@ struct geneve_sock *geneve_sock_add(stru
if (no_share) /* Return error if sharing is not allowed. */
return ERR_PTR(-EINVAL);

+ spin_lock(&gn->sock_lock);
gs = geneve_find_sock(net, port);
- if (gs) {
- if (gs->rcv == rcv)
- atomic_inc(&gs->refcnt);
- else
+ if (gs && ((gs->rcv != rcv) ||
+ !atomic_add_unless(&gs->refcnt, 1, 0)))
gs = ERR_PTR(-EBUSY);
- } else {
+ spin_unlock(&gn->sock_lock);
+
+ if (!gs)
gs = ERR_PTR(-EINVAL);
- }

return gs;
}