Re: Hung task when calling clone() due to netfilter/slab

[Eric Dumazet <eric.dumazet@xxxxxxxxx>]

Le mardi 17 janvier 2012 à 09:27 -0600, Christoph Lameter a écrit :

> Subject: slub: Do not hold slub_lock when calling sysfs_slab_add()
> 
> sysfs_slab_add() calls various sysfs functions that actually may
> end up in userspace doing all sorts of things.
> 
> Release the slub_lock after adding the kmem_cache structure to the list.
> At that point the address of the kmem_cache is not known so we are
> guaranteed exlusive access to the following modifications to the
> kmem_cache structure.
> 
> If the sysfs_slab_add fails then reacquire the slub_lock to
> remove the kmem_cache structure from the list.
> 
> Reported-by: Sasha Levin <levinsasha928@xxxxxxxxx>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
> 
> ---
>  mm/slub.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2012-01-17 03:07:11.140010438 -0600
> +++ linux-2.6/mm/slub.c	2012-01-17 03:26:06.799986908 -0600
> @@ -3929,13 +3929,14 @@ struct kmem_cache *kmem_cache_create(con
>  		if (kmem_cache_open(s, n,
>  				size, align, flags, ctor)) {
>  			list_add(&s->list, &slab_caches);
> +			up_write(&slub_lock);
>  			if (sysfs_slab_add(s)) {
> +				down_write(&slub_lock);
>  				list_del(&s->list);
>  				kfree(n);
>  				kfree(s);
>  				goto err;
>  			}
> -			up_write(&slub_lock);
>  			return s;
>  		}
>  		kfree(n);

Thanks !

Acked-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>


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