tun: fix a crash bug and a memory leak
This patch fixes a crash
tun_chr_close -> netdev_run_todo -> tun_free_netdev -> sk_release_kernel ->
sock_release -> iput(SOCK_INODE(sock))
introduced by commit 1ab5ecb90cb6a3df1476e052f76a6e8f6511cb3d
The problem is that this socket is embedded in struct tun_struct, it has
no inode, iput is called on invalid inode, which modifies invalid memory
and optionally causes a crash.
sock_release also decrements sockets_in_use, this causes a bug that
"sockets: used" field in /proc/*/net/sockstat keeps on decreasing when
creating and closing tun devices.
This patch introduces a flag SOCK_EXTERNALLY_ALLOCATED that instructs
sock_release to not free the inode and not decrement sockets_in_use,
fixing both memory corruption and sockets_in_use underflow.
It should be backported to 3.3 an 3.4 stabke.
Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/socket.c b/net/socket.c
index 6e0ccc0..0452dca 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -522,6 +522,9 @@
if (rcu_dereference_protected(sock->wq, 1)->fasync_list)
printk(KERN_ERR "sock_release: fasync list not empty!\n");
+ if (test_bit(SOCK_EXTERNALLY_ALLOCATED, &sock->flags))
+ return;
+
this_cpu_sub(sockets_in_use, 1);
if (!sock->file) {
iput(SOCK_INODE(sock));