Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b09e786b authored by Mikulas Patocka's avatar Mikulas Patocka Committed by David S. Miller
Browse files

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 1ab5ecb9

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: default avatarMikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: stable@kernel.org
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 521f5490

drivers/net/tun.c

+3 −0
Original line number Diff line number Diff line
@@ -358,6 +358,8 @@ static void tun_free_netdev(struct net_device *dev) 
{

	struct tun_struct *tun = netdev_priv(dev);



	BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED, &tun->socket.flags));



	sk_release_kernel(tun->socket.sk);

}
@@ -1115,6 +1117,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) 
		tun->flags = flags;

		tun->txflt.count = 0;

		tun->vnet_hdr_sz = sizeof(struct virtio_net_hdr);

		set_bit(SOCK_EXTERNALLY_ALLOCATED, &tun->socket.flags);



		err = -ENOMEM;

		sk = sk_alloc(&init_net, AF_UNSPEC, GFP_KERNEL, &tun_proto);

include/linux/net.h

+1 −0
Original line number Diff line number Diff line
@@ -72,6 +72,7 @@ struct net; 
#define SOCK_NOSPACE		2

#define SOCK_PASSCRED		3

#define SOCK_PASSSEC		4

#define SOCK_EXTERNALLY_ALLOCATED 5



#ifndef ARCH_HAS_SOCKET_TYPES

/**

net/socket.c

+3 −0
Original line number Diff line number Diff line
@@ -522,6 +522,9 @@ void sock_release(struct socket *sock) 
	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));