Revision 774a1221e862b343388347bac9b318767336b20b authored by Tejun Heo on 16 January 2013, 02:52:51 UTC, committed by Linus Torvalds on 16 January 2013, 17:05:33 UTC
If the default iosched is built as module, the kernel may deadlock while trying to load the iosched module on device probe if the probing was running off async. This is because async_synchronize_full() at the end of module init ends up waiting for the async job which initiated the module loading. async A modprobe 1. finds a device 2. registers the block device 3. request_module(default iosched) 4. modprobe in userland 5. load and init module 6. async_synchronize_full() Async A waits for modprobe to finish in request_module() and modprobe waits for async A to finish in async_synchronize_full(). Because there's no easy to track dependency once control goes out to userland, implementing properly nested flushing is difficult. For now, make module init perform async_synchronize_full() iff module init has queued async jobs as suggested by Linus. This avoids the described deadlock because iosched module doesn't use async and thus wouldn't invoke async_synchronize_full(). This is hacky and incomplete. It will deadlock if async module loading nests; however, this works around the known problem case and seems to be the best of bad options. For more details, please refer to the following thread. http://thread.gmane.org/gmane.linux.kernel/1420814 Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Alex Riesen <raa.lkml@gmail.com> Tested-by: Ming Lei <ming.lei@canonical.com> Tested-by: Alex Riesen <raa.lkml@gmail.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 406089d
br_ioctl.c
/*
* Ioctl handler
* Linux ethernet bridge
*
* Authors:
* Lennert Buytenhek <buytenh@gnu.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/capability.h>
#include <linux/kernel.h>
#include <linux/if_bridge.h>
#include <linux/netdevice.h>
#include <linux/slab.h>
#include <linux/times.h>
#include <net/net_namespace.h>
#include <asm/uaccess.h>
#include "br_private.h"
/* called with RTNL */
static int get_bridge_ifindices(struct net *net, int *indices, int num)
{
struct net_device *dev;
int i = 0;
for_each_netdev(net, dev) {
if (i >= num)
break;
if (dev->priv_flags & IFF_EBRIDGE)
indices[i++] = dev->ifindex;
}
return i;
}
/* called with RTNL */
static void get_port_ifindices(struct net_bridge *br, int *ifindices, int num)
{
struct net_bridge_port *p;
list_for_each_entry(p, &br->port_list, list) {
if (p->port_no < num)
ifindices[p->port_no] = p->dev->ifindex;
}
}
/*
* Format up to a page worth of forwarding table entries
* userbuf -- where to copy result
* maxnum -- maximum number of entries desired
* (limited to a page for sanity)
* offset -- number of records to skip
*/
static int get_fdb_entries(struct net_bridge *br, void __user *userbuf,
unsigned long maxnum, unsigned long offset)
{
int num;
void *buf;
size_t size;
/* Clamp size to PAGE_SIZE, test maxnum to avoid overflow */
if (maxnum > PAGE_SIZE/sizeof(struct __fdb_entry))
maxnum = PAGE_SIZE/sizeof(struct __fdb_entry);
size = maxnum * sizeof(struct __fdb_entry);
buf = kmalloc(size, GFP_USER);
if (!buf)
return -ENOMEM;
num = br_fdb_fillbuf(br, buf, maxnum, offset);
if (num > 0) {
if (copy_to_user(userbuf, buf, num*sizeof(struct __fdb_entry)))
num = -EFAULT;
}
kfree(buf);
return num;
}
/* called with RTNL */
static int add_del_if(struct net_bridge *br, int ifindex, int isadd)
{
struct net *net = dev_net(br->dev);
struct net_device *dev;
int ret;
if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
return -EPERM;
dev = __dev_get_by_index(net, ifindex);
if (dev == NULL)
return -EINVAL;
if (isadd)
ret = br_add_if(br, dev);
else
ret = br_del_if(br, dev);
return ret;
}
/*
* Legacy ioctl's through SIOCDEVPRIVATE
* This interface is deprecated because it was too difficult to
* to do the translation for 32/64bit ioctl compatibility.
*/
static int old_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
struct net_bridge *br = netdev_priv(dev);
unsigned long args[4];
if (copy_from_user(args, rq->ifr_data, sizeof(args)))
return -EFAULT;
switch (args[0]) {
case BRCTL_ADD_IF:
case BRCTL_DEL_IF:
return add_del_if(br, args[1], args[0] == BRCTL_ADD_IF);
case BRCTL_GET_BRIDGE_INFO:
{
struct __bridge_info b;
memset(&b, 0, sizeof(struct __bridge_info));
rcu_read_lock();
memcpy(&b.designated_root, &br->designated_root, 8);
memcpy(&b.bridge_id, &br->bridge_id, 8);
b.root_path_cost = br->root_path_cost;
b.max_age = jiffies_to_clock_t(br->max_age);
b.hello_time = jiffies_to_clock_t(br->hello_time);
b.forward_delay = br->forward_delay;
b.bridge_max_age = br->bridge_max_age;
b.bridge_hello_time = br->bridge_hello_time;
b.bridge_forward_delay = jiffies_to_clock_t(br->bridge_forward_delay);
b.topology_change = br->topology_change;
b.topology_change_detected = br->topology_change_detected;
b.root_port = br->root_port;
b.stp_enabled = (br->stp_enabled != BR_NO_STP);
b.ageing_time = jiffies_to_clock_t(br->ageing_time);
b.hello_timer_value = br_timer_value(&br->hello_timer);
b.tcn_timer_value = br_timer_value(&br->tcn_timer);
b.topology_change_timer_value = br_timer_value(&br->topology_change_timer);
b.gc_timer_value = br_timer_value(&br->gc_timer);
rcu_read_unlock();
if (copy_to_user((void __user *)args[1], &b, sizeof(b)))
return -EFAULT;
return 0;
}
case BRCTL_GET_PORT_LIST:
{
int num, *indices;
num = args[2];
if (num < 0)
return -EINVAL;
if (num == 0)
num = 256;
if (num > BR_MAX_PORTS)
num = BR_MAX_PORTS;
indices = kcalloc(num, sizeof(int), GFP_KERNEL);
if (indices == NULL)
return -ENOMEM;
get_port_ifindices(br, indices, num);
if (copy_to_user((void __user *)args[1], indices, num*sizeof(int)))
num = -EFAULT;
kfree(indices);
return num;
}
case BRCTL_SET_BRIDGE_FORWARD_DELAY:
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
return br_set_forward_delay(br, args[1]);
case BRCTL_SET_BRIDGE_HELLO_TIME:
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
return br_set_hello_time(br, args[1]);
case BRCTL_SET_BRIDGE_MAX_AGE:
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
return br_set_max_age(br, args[1]);
case BRCTL_SET_AGEING_TIME:
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
br->ageing_time = clock_t_to_jiffies(args[1]);
return 0;
case BRCTL_GET_PORT_INFO:
{
struct __port_info p;
struct net_bridge_port *pt;
rcu_read_lock();
if ((pt = br_get_port(br, args[2])) == NULL) {
rcu_read_unlock();
return -EINVAL;
}
memset(&p, 0, sizeof(struct __port_info));
memcpy(&p.designated_root, &pt->designated_root, 8);
memcpy(&p.designated_bridge, &pt->designated_bridge, 8);
p.port_id = pt->port_id;
p.designated_port = pt->designated_port;
p.path_cost = pt->path_cost;
p.designated_cost = pt->designated_cost;
p.state = pt->state;
p.top_change_ack = pt->topology_change_ack;
p.config_pending = pt->config_pending;
p.message_age_timer_value = br_timer_value(&pt->message_age_timer);
p.forward_delay_timer_value = br_timer_value(&pt->forward_delay_timer);
p.hold_timer_value = br_timer_value(&pt->hold_timer);
rcu_read_unlock();
if (copy_to_user((void __user *)args[1], &p, sizeof(p)))
return -EFAULT;
return 0;
}
case BRCTL_SET_BRIDGE_STP_STATE:
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
br_stp_set_enabled(br, args[1]);
return 0;
case BRCTL_SET_BRIDGE_PRIORITY:
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
spin_lock_bh(&br->lock);
br_stp_set_bridge_priority(br, args[1]);
spin_unlock_bh(&br->lock);
return 0;
case BRCTL_SET_PORT_PRIORITY:
{
struct net_bridge_port *p;
int ret;
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
spin_lock_bh(&br->lock);
if ((p = br_get_port(br, args[1])) == NULL)
ret = -EINVAL;
else
ret = br_stp_set_port_priority(p, args[2]);
spin_unlock_bh(&br->lock);
return ret;
}
case BRCTL_SET_PATH_COST:
{
struct net_bridge_port *p;
int ret;
if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
spin_lock_bh(&br->lock);
if ((p = br_get_port(br, args[1])) == NULL)
ret = -EINVAL;
else
ret = br_stp_set_path_cost(p, args[2]);
spin_unlock_bh(&br->lock);
return ret;
}
case BRCTL_GET_FDB_ENTRIES:
return get_fdb_entries(br, (void __user *)args[1],
args[2], args[3]);
}
return -EOPNOTSUPP;
}
static int old_deviceless(struct net *net, void __user *uarg)
{
unsigned long args[3];
if (copy_from_user(args, uarg, sizeof(args)))
return -EFAULT;
switch (args[0]) {
case BRCTL_GET_VERSION:
return BRCTL_VERSION;
case BRCTL_GET_BRIDGES:
{
int *indices;
int ret = 0;
if (args[2] >= 2048)
return -ENOMEM;
indices = kcalloc(args[2], sizeof(int), GFP_KERNEL);
if (indices == NULL)
return -ENOMEM;
args[2] = get_bridge_ifindices(net, indices, args[2]);
ret = copy_to_user((void __user *)args[1], indices, args[2]*sizeof(int))
? -EFAULT : args[2];
kfree(indices);
return ret;
}
case BRCTL_ADD_BRIDGE:
case BRCTL_DEL_BRIDGE:
{
char buf[IFNAMSIZ];
if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
return -EPERM;
if (copy_from_user(buf, (void __user *)args[1], IFNAMSIZ))
return -EFAULT;
buf[IFNAMSIZ-1] = 0;
if (args[0] == BRCTL_ADD_BRIDGE)
return br_add_bridge(net, buf);
return br_del_bridge(net, buf);
}
}
return -EOPNOTSUPP;
}
int br_ioctl_deviceless_stub(struct net *net, unsigned int cmd, void __user *uarg)
{
switch (cmd) {
case SIOCGIFBR:
case SIOCSIFBR:
return old_deviceless(net, uarg);
case SIOCBRADDBR:
case SIOCBRDELBR:
{
char buf[IFNAMSIZ];
if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
return -EPERM;
if (copy_from_user(buf, uarg, IFNAMSIZ))
return -EFAULT;
buf[IFNAMSIZ-1] = 0;
if (cmd == SIOCBRADDBR)
return br_add_bridge(net, buf);
return br_del_bridge(net, buf);
}
}
return -EOPNOTSUPP;
}
int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
struct net_bridge *br = netdev_priv(dev);
switch(cmd) {
case SIOCDEVPRIVATE:
return old_dev_ioctl(dev, rq, cmd);
case SIOCBRADDIF:
case SIOCBRDELIF:
return add_del_if(br, rq->ifr_ifindex, cmd == SIOCBRADDIF);
}
br_debug(br, "Bridge does not support ioctl 0x%x\n", cmd);
return -EOPNOTSUPP;
}
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