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Date: Mon, 10 Mar 2014 14:51:27 +0800
From: Fan Du <fan.du@...driver.com>
To: Eric Dumazet <eric.dumazet@...il.com>
CC: Jakub Kicinski <moorray3@...pl>, <netdev@...r.kernel.org>,
Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: net-next: NULL pointer dereference on adding a net namespace
and a system freeze
On 2014年03月10日 12:09, Eric Dumazet wrote:
> On Sun, 2014-03-09 at 21:02 -0700, Eric Dumazet wrote:
>> On Mon, 2014-03-10 at 01:44 +0100, Jakub Kicinski wrote:
>>> Hi!
>>>
>>> Running Fedora 20 with net-next I get the following warning when
>>> libvirt or rtkit comes up:
>>>
>>> [ 272.143488] kmem_cache_sanity_check (flow_cache): Cache name already exists.
>>> [ 272.143586] CPU: 0 PID: 975 Comm: libvirtd Not tainted 3.14.0-rc5+ #1
>>> [ 272.143589] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
>>> [ 272.143591] 0000000000000000 ffff88003ceadba0 ffffffff8167baf0 ffff88003db3d300
>>> [ 272.143595] ffff88003ceadc18 ffffffff8117795b ffff88003ceadbc8 ffff88003b235158
>>> [ 272.143599] 0000000000000000 0000000000040000 0000000000000068 0000000000000000
>>> [ 272.143602] Call Trace:
>>> [ 272.143610] [<ffffffff8167baf0>] dump_stack+0x4d/0x66
>>> [ 272.143615] [<ffffffff8117795b>] kmem_cache_create_memcg+0x12b/0x420
>>> [ 272.143618] [<ffffffff81177c7b>] kmem_cache_create+0x2b/0x30
>>> [ 272.143622] [<ffffffff815c4a0e>] flow_cache_init+0x2e/0x2b0
>>> [ 272.143626] [<ffffffff8164b017>] xfrm_net_init+0x227/0x360
>>> [ 272.143629] [<ffffffff8164af41>] ? xfrm_net_init+0x151/0x360
>>> [ 272.143632] [<ffffffff815a5921>] ops_init+0x41/0x150
>>> [ 272.143635] [<ffffffff815a5aa3>] setup_net+0x73/0x110
>>> [ 272.143638] [<ffffffff815a5fe2>] copy_net_ns+0x72/0x100
>>> [ 272.143642] [<ffffffff810943f9>] create_new_namespaces+0xf9/0x190
>>> [ 272.143645] [<ffffffff81094560>] copy_namespaces+0xd0/0xf0
>>> [ 272.143648] [<ffffffff81094495>] ? copy_namespaces+0x5/0xf0
>>> [ 272.143651] [<ffffffff81069be0>] copy_process.part.31+0x950/0x1b30
>>> [ 272.143655] [<ffffffff8106af95>] do_fork+0xd5/0x370
>>> [ 272.143658] [<ffffffff811c1b2d>] ? __fput+0x17d/0x240
>>> [ 272.143662] [<ffffffff8110440c>] ? __audit_syscall_entry+0x9c/0xf0
>>> [ 272.143665] [<ffffffff8106b2b6>] SyS_clone+0x16/0x20
>>> [ 272.143669] [<ffffffff8168cf19>] stub_clone+0x69/0x90
>>> [ 272.143673] [<ffffffff8168cb69>] ? system_call_fastpath+0x16/0x1b
>>>
>>>
>>> When I try to add a netns with
>>> # ip netns add abcd
>>> I it dies with:
>>
>>
>> Yep, commit ca925cf1534ebcec332c08719a7dee6ee1782ce4 is buggy.
>>
>> flowcache: Make flow cache name space aware
>>
>> Inserting a entry into flowcache, or flushing flowcache should be based
>> on per net scope. The reason to do so is flushing operation from fat
>> netns crammed with flow entries will also making the slim netns with only
>> a few flow cache entries go away in original implementation.
>>
>> Since flowcache is tightly coupled with IPsec, so it would be easier to
>> put flow cache global parameters into xfrm namespace part. And one last
>> thing needs to do is bumping flow cache genid, and flush flow cache should
>> also be made in per net style.
>>
>> Signed-off-by: Fan Du<fan.du@...driver.com>
>> Signed-off-by: Steffen Klassert<steffen.klassert@...unet.com>
>>
>> I fail to understand why the kmem_cache must be private to a netns.
Sorry, I didn't turn on CONFIG_DEBUG_VM before...
Sometimes network activity only on netns could trigger bugs like memory leakage,
using per-netns kmem_cache could help to identify which netns to be blamed.
Anyway if this is inappropriate, let's make it global as you did below.
> Could you please try the following patch ?
>
Tested-by: Fan Du <fan.du@...driver.com>
> diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
> index 51f0dce7b643..3492434baf88 100644
> --- a/include/net/netns/xfrm.h
> +++ b/include/net/netns/xfrm.h
> @@ -64,7 +64,6 @@ struct netns_xfrm {
>
> /* flow cache part */
> struct flow_cache flow_cache_global;
> - struct kmem_cache *flow_cachep;
> atomic_t flow_cache_genid;
> struct list_head flow_cache_gc_list;
> spinlock_t flow_cache_gc_lock;
> diff --git a/net/core/flow.c b/net/core/flow.c
> index 344a184011fd..102f8ea2eb6e 100644
> --- a/net/core/flow.c
> +++ b/net/core/flow.c
> @@ -45,6 +45,8 @@ struct flow_flush_info {
> struct completion completion;
> };
>
> +static struct kmem_cache *flow_cachep __read_mostly;
> +
> #define flow_cache_hash_size(cache) (1<< (cache)->hash_shift)
> #define FLOW_HASH_RND_PERIOD (10 * 60 * HZ)
>
> @@ -75,7 +77,7 @@ static void flow_entry_kill(struct flow_cache_entry *fle,
> {
> if (fle->object)
> fle->object->ops->delete(fle->object);
> - kmem_cache_free(xfrm->flow_cachep, fle);
> + kmem_cache_free(flow_cachep, fle);
> }
>
> static void flow_cache_gc_task(struct work_struct *work)
> @@ -230,7 +232,7 @@ flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
> if (fcp->hash_count> fc->high_watermark)
> flow_cache_shrink(fc, fcp);
>
> - fle = kmem_cache_alloc(net->xfrm.flow_cachep, GFP_ATOMIC);
> + fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
> if (fle) {
> fle->net = net;
> fle->family = family;
> @@ -435,10 +437,10 @@ int flow_cache_init(struct net *net)
> int i;
> struct flow_cache *fc =&net->xfrm.flow_cache_global;
>
> - /* Initialize per-net flow cache global variables here */
> - net->xfrm.flow_cachep = kmem_cache_create("flow_cache",
> - sizeof(struct flow_cache_entry),
> - 0, SLAB_PANIC, NULL);
> + if (!flow_cachep)
> + flow_cachep = kmem_cache_create("flow_cache",
> + sizeof(struct flow_cache_entry),
> + 0, SLAB_PANIC, NULL);
> spin_lock_init(&net->xfrm.flow_cache_gc_lock);
> INIT_LIST_HEAD(&net->xfrm.flow_cache_gc_list);
> INIT_WORK(&net->xfrm.flow_cache_gc_work, flow_cache_gc_task);
>
>
>
--
浮沉随浪只记今朝笑
--fan
--
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