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linux-next/drivers/net/dummy.c
dingtianhong 2c8a01894a dummy: fix oops when loading the dummy failed
We rename the dummy in modprobe.conf like this:

install dummy0 /sbin/modprobe -o dummy0 --ignore-install dummy
install dummy1 /sbin/modprobe -o dummy1 --ignore-install dummy

We got oops when we run the command:

modprobe dummy0
modprobe dummy1

------------[ cut here ]------------

[ 3302.187584] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[ 3302.195411] IP: [<ffffffff813fe62a>] __rtnl_link_unregister+0x9a/0xd0
[ 3302.201844] PGD 85c94a067 PUD 8517bd067 PMD 0
[ 3302.206305] Oops: 0002 [#1] SMP
[ 3302.299737] task: ffff88105ccea300 ti: ffff880eba4a0000 task.ti: ffff880eba4a0000
[ 3302.307186] RIP: 0010:[<ffffffff813fe62a>]  [<ffffffff813fe62a>] __rtnl_link_unregister+0x9a/0xd0
[ 3302.316044] RSP: 0018:ffff880eba4a1dd8  EFLAGS: 00010246
[ 3302.321332] RAX: 0000000000000000 RBX: ffffffff81a9d738 RCX: 0000000000000002
[ 3302.328436] RDX: 0000000000000000 RSI: ffffffffa04d602c RDI: ffff880eba4a1dd8
[ 3302.335541] RBP: ffff880eba4a1e18 R08: dead000000200200 R09: dead000000100100
[ 3302.342644] R10: 0000000000000080 R11: 0000000000000003 R12: ffffffff81a9d788
[ 3302.349748] R13: ffffffffa04d7020 R14: ffffffff81a9d670 R15: ffff880eba4a1dd8
[ 3302.364910] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3302.370630] CR2: 0000000000000008 CR3: 000000085e15e000 CR4: 00000000000427e0
[ 3302.377734] DR0: 0000000000000003 DR1: 00000000000000b0 DR2: 0000000000000001
[ 3302.384838] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 3302.391940] Stack:
[ 3302.393944]  ffff880eba4a1dd8 ffff880eba4a1dd8 ffff880eba4a1e18 ffffffffa04d70c0
[ 3302.401350]  00000000ffffffef ffffffffa01a8000 0000000000000000 ffffffff816111c8
[ 3302.408758]  ffff880eba4a1e48 ffffffffa01a80be ffff880eba4a1e48 ffffffffa04d70c0
[ 3302.416164] Call Trace:
[ 3302.418605]  [<ffffffffa01a8000>] ? 0xffffffffa01a7fff
[ 3302.423727]  [<ffffffffa01a80be>] dummy_init_module+0xbe/0x1000 [dummy0]
[ 3302.430405]  [<ffffffffa01a8000>] ? 0xffffffffa01a7fff
[ 3302.435535]  [<ffffffff81000322>] do_one_initcall+0x152/0x1b0
[ 3302.441263]  [<ffffffff810ab24b>] do_init_module+0x7b/0x200
[ 3302.446824]  [<ffffffff810ad3d2>] load_module+0x4e2/0x530
[ 3302.452215]  [<ffffffff8127ae40>] ? ddebug_dyndbg_boot_param_cb+0x60/0x60
[ 3302.458979]  [<ffffffff810ad5f1>] SyS_init_module+0xd1/0x130
[ 3302.464627]  [<ffffffff814b9652>] system_call_fastpath+0x16/0x1b
[ 3302.490090] RIP  [<ffffffff813fe62a>] __rtnl_link_unregister+0x9a/0xd0
[ 3302.496607]  RSP <ffff880eba4a1dd8>
[ 3302.500084] CR2: 0000000000000008
[ 3302.503466] ---[ end trace 8342d49cd49f78ed ]---

The reason is that when loading dummy, if __rtnl_link_register() return failed,
the init_module should return and avoid take the wrong path.

Signed-off-by: Tan Xiaojun <tanxiaojun@huawei.com>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2013-07-11 11:59:20 -07:00

213 lines
4.9 KiB
C

/* dummy.c: a dummy net driver
The purpose of this driver is to provide a device to point a
route through, but not to actually transmit packets.
Why? If you have a machine whose only connection is an occasional
PPP/SLIP/PLIP link, you can only connect to your own hostname
when the link is up. Otherwise you have to use localhost.
This isn't very consistent.
One solution is to set up a dummy link using PPP/SLIP/PLIP,
but this seems (to me) too much overhead for too little gain.
This driver provides a small alternative. Thus you can do
[when not running slip]
ifconfig dummy slip.addr.ess.here up
[to go to slip]
ifconfig dummy down
dip whatever
This was written by looking at Donald Becker's skeleton driver
and the loopback driver. I then threw away anything that didn't
apply! Thanks to Alan Cox for the key clue on what to do with
misguided packets.
Nick Holloway, 27th May 1994
[I tweaked this explanation a little but that's all]
Alan Cox, 30th May 1994
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/rtnetlink.h>
#include <net/rtnetlink.h>
#include <linux/u64_stats_sync.h>
static int numdummies = 1;
/* fake multicast ability */
static void set_multicast_list(struct net_device *dev)
{
}
struct pcpu_dstats {
u64 tx_packets;
u64 tx_bytes;
struct u64_stats_sync syncp;
};
static struct rtnl_link_stats64 *dummy_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *stats)
{
int i;
for_each_possible_cpu(i) {
const struct pcpu_dstats *dstats;
u64 tbytes, tpackets;
unsigned int start;
dstats = per_cpu_ptr(dev->dstats, i);
do {
start = u64_stats_fetch_begin_bh(&dstats->syncp);
tbytes = dstats->tx_bytes;
tpackets = dstats->tx_packets;
} while (u64_stats_fetch_retry_bh(&dstats->syncp, start));
stats->tx_bytes += tbytes;
stats->tx_packets += tpackets;
}
return stats;
}
static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
u64_stats_update_begin(&dstats->syncp);
dstats->tx_packets++;
dstats->tx_bytes += skb->len;
u64_stats_update_end(&dstats->syncp);
dev_kfree_skb(skb);
return NETDEV_TX_OK;
}
static int dummy_dev_init(struct net_device *dev)
{
dev->dstats = alloc_percpu(struct pcpu_dstats);
if (!dev->dstats)
return -ENOMEM;
return 0;
}
static void dummy_dev_uninit(struct net_device *dev)
{
free_percpu(dev->dstats);
}
static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
{
if (new_carrier)
netif_carrier_on(dev);
else
netif_carrier_off(dev);
return 0;
}
static const struct net_device_ops dummy_netdev_ops = {
.ndo_init = dummy_dev_init,
.ndo_uninit = dummy_dev_uninit,
.ndo_start_xmit = dummy_xmit,
.ndo_validate_addr = eth_validate_addr,
.ndo_set_rx_mode = set_multicast_list,
.ndo_set_mac_address = eth_mac_addr,
.ndo_get_stats64 = dummy_get_stats64,
.ndo_change_carrier = dummy_change_carrier,
};
static void dummy_setup(struct net_device *dev)
{
ether_setup(dev);
/* Initialize the device structure. */
dev->netdev_ops = &dummy_netdev_ops;
dev->destructor = free_netdev;
/* Fill in device structure with ethernet-generic values. */
dev->tx_queue_len = 0;
dev->flags |= IFF_NOARP;
dev->flags &= ~IFF_MULTICAST;
dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
eth_hw_addr_random(dev);
}
static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
{
if (tb[IFLA_ADDRESS]) {
if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
return -EINVAL;
if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
return -EADDRNOTAVAIL;
}
return 0;
}
static struct rtnl_link_ops dummy_link_ops __read_mostly = {
.kind = "dummy",
.setup = dummy_setup,
.validate = dummy_validate,
};
/* Number of dummy devices to be set up by this module. */
module_param(numdummies, int, 0);
MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
static int __init dummy_init_one(void)
{
struct net_device *dev_dummy;
int err;
dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
if (!dev_dummy)
return -ENOMEM;
dev_dummy->rtnl_link_ops = &dummy_link_ops;
err = register_netdevice(dev_dummy);
if (err < 0)
goto err;
return 0;
err:
free_netdev(dev_dummy);
return err;
}
static int __init dummy_init_module(void)
{
int i, err = 0;
rtnl_lock();
err = __rtnl_link_register(&dummy_link_ops);
if (err < 0)
goto out;
for (i = 0; i < numdummies && !err; i++) {
err = dummy_init_one();
cond_resched();
}
if (err < 0)
__rtnl_link_unregister(&dummy_link_ops);
out:
rtnl_unlock();
return err;
}
static void __exit dummy_cleanup_module(void)
{
rtnl_link_unregister(&dummy_link_ops);
}
module_init(dummy_init_module);
module_exit(dummy_cleanup_module);
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK("dummy");