system/linux
system/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux synced 2024-11-05 18:23:50 +00:00
Code Issues Projects Releases Packages Wiki Activity

Merge branch 'ipv6_percpu_rt_deadlock'

Browse source 
Martin KaFai Lau says:

====================
ipv6: Fix a potential deadlock when creating pcpu rt

v1 -> v2:
A minor change in the commit message of patch 2.

This patch series fixes a potential deadlock when creating a pcpu rt.
It happens when dst_alloc() decided to run gc. Something like this:

read_lock(&table->tb6_lock);
ip6_rt_pcpu_alloc()
=> dst_alloc()
=> ip6_dst_gc()
=> write_lock(&table->tb6_lock); /* oops */

Patch 1 and 2 are some prep works.
Patch 3 is the fix.

Original report: https://bugzilla.kernel.org/show_bug.cgi?id=102291
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2015-08-17 14:28:04 -07:00
commit 1f979b117b
2 changed files with 57 additions and 24 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
net/ipv6/ip6_fib.c
View file

@ -172,6 +172,8 @@ static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
*ppcpu_rt = NULL;
}
}
non_pcpu_rt->rt6i_pcpu = NULL;
}
static void rt6_release(struct rt6_info *rt)

79
net/ipv6/route.c
View file

@ -318,8 +318,7 @@ static const struct rt6_info ip6_blk_hole_entry_template = {
/* allocate dst with ip6_dst_ops */
static struct rt6_info *__ip6_dst_alloc(struct net *net,
struct net_device *dev,
int flags,
struct fib6_table *table)
int flags)
{
struct rt6_info *rt = dst_alloc(&net->ipv6.ip6_dst_ops, dev,
0, DST_OBSOLETE_FORCE_CHK, flags);
@ -336,10 +335,9 @@ static struct rt6_info *__ip6_dst_alloc(struct net *net,
static struct rt6_info *ip6_dst_alloc(struct net *net,
struct net_device *dev,
int flags,
struct fib6_table *table)
int flags)
{
struct rt6_info *rt = __ip6_dst_alloc(net, dev, flags, table);
struct rt6_info *rt = __ip6_dst_alloc(net, dev, flags);
if (rt) {
rt->rt6i_pcpu = alloc_percpu_gfp(struct rt6_info *, GFP_ATOMIC);
@ -950,8 +948,7 @@ static struct rt6_info *ip6_rt_cache_alloc(struct rt6_info *ort,
if (ort->rt6i_flags & (RTF_CACHE | RTF_PCPU))
ort = (struct rt6_info *)ort->dst.from;
rt = __ip6_dst_alloc(dev_net(ort->dst.dev), ort->dst.dev,
0, ort->rt6i_table);
rt = __ip6_dst_alloc(dev_net(ort->dst.dev), ort->dst.dev, 0);
if (!rt)
return NULL;
@ -983,8 +980,7 @@ static struct rt6_info *ip6_rt_pcpu_alloc(struct rt6_info *rt)
struct rt6_info *pcpu_rt;
pcpu_rt = __ip6_dst_alloc(dev_net(rt->dst.dev),
rt->dst.dev, rt->dst.flags,
rt->rt6i_table);
rt->dst.dev, rt->dst.flags);
if (!pcpu_rt)
return NULL;
@ -997,32 +993,53 @@ static struct rt6_info *ip6_rt_pcpu_alloc(struct rt6_info *rt)
/* It should be called with read_lock_bh(&tb6_lock) acquired */
static struct rt6_info *rt6_get_pcpu_route(struct rt6_info *rt)
{
struct rt6_info *pcpu_rt, *prev, **p;
struct rt6_info *pcpu_rt, **p;
p = this_cpu_ptr(rt->rt6i_pcpu);
pcpu_rt = *p;
if (pcpu_rt)
goto done;
if (pcpu_rt) {
dst_hold(&pcpu_rt->dst);
rt6_dst_from_metrics_check(pcpu_rt);
}
return pcpu_rt;
}
static struct rt6_info *rt6_make_pcpu_route(struct rt6_info *rt)
{
struct fib6_table *table = rt->rt6i_table;
struct rt6_info *pcpu_rt, *prev, **p;
pcpu_rt = ip6_rt_pcpu_alloc(rt);
if (!pcpu_rt) {
struct net *net = dev_net(rt->dst.dev);
pcpu_rt = net->ipv6.ip6_null_entry;
goto done;
dst_hold(&net->ipv6.ip6_null_entry->dst);
return net->ipv6.ip6_null_entry;
}
prev = cmpxchg(p, NULL, pcpu_rt);
if (prev) {
/* If someone did it before us, return prev instead */
read_lock_bh(&table->tb6_lock);
if (rt->rt6i_pcpu) {
p = this_cpu_ptr(rt->rt6i_pcpu);
prev = cmpxchg(p, NULL, pcpu_rt);
if (prev) {
/* If someone did it before us, return prev instead */
dst_destroy(&pcpu_rt->dst);
pcpu_rt = prev;
}
} else {
/* rt has been removed from the fib6 tree
* before we have a chance to acquire the read_lock.
* In this case, don't brother to create a pcpu rt
* since rt is going away anyway. The next
* dst_check() will trigger a re-lookup.
*/
dst_destroy(&pcpu_rt->dst);
pcpu_rt = prev;
pcpu_rt = rt;
}
done:
dst_hold(&pcpu_rt->dst);
rt6_dst_from_metrics_check(pcpu_rt);
read_unlock_bh(&table->tb6_lock);
return pcpu_rt;
}
@ -1097,9 +1114,22 @@ static struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
rt->dst.lastuse = jiffies;
rt->dst.__use++;
pcpu_rt = rt6_get_pcpu_route(rt);
read_unlock_bh(&table->tb6_lock);
if (pcpu_rt) {
read_unlock_bh(&table->tb6_lock);
} else {
/* We have to do the read_unlock first
* because rt6_make_pcpu_route() may trigger
* ip6_dst_gc() which will take the write_lock.
*/
dst_hold(&rt->dst);
read_unlock_bh(&table->tb6_lock);
pcpu_rt = rt6_make_pcpu_route(rt);
dst_release(&rt->dst);
}
return pcpu_rt;
}
}
@ -1555,7 +1585,7 @@ struct dst_entry *icmp6_dst_alloc(struct net_device *dev,
if (unlikely(!idev))
return ERR_PTR(-ENODEV);
rt = ip6_dst_alloc(net, dev, 0, NULL);
rt = ip6_dst_alloc(net, dev, 0);
if (unlikely(!rt)) {
in6_dev_put(idev);
dst = ERR_PTR(-ENOMEM);
@ -1742,7 +1772,8 @@ int ip6_route_add(struct fib6_config *cfg)
if (!table)
goto out;
rt = ip6_dst_alloc(net, NULL, (cfg->fc_flags & RTF_ADDRCONF) ? 0 : DST_NOCOUNT, table);
rt = ip6_dst_alloc(net, NULL,
(cfg->fc_flags & RTF_ADDRCONF) ? 0 : DST_NOCOUNT);
if (!rt) {
err = -ENOMEM;
@ -2399,7 +2430,7 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev,
{
struct net *net = dev_net(idev->dev);
struct rt6_info *rt = ip6_dst_alloc(net, net->loopback_dev,
DST_NOCOUNT, NULL);
DST_NOCOUNT);
if (!rt)
return ERR_PTR(-ENOMEM);