linux-kernel - Re: [PATCH] slob: Check for NULL pointer before calling ctor()

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Date:	Tue, 05 Feb 2013 09:16:51 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>
Subject: Re: [PATCH] slob: Check for NULL pointer before calling ctor()

Ping?

-- Steve


On Thu, 2013-01-17 at 12:13 -0500, Steven Rostedt wrote:
> [ Sorry for the duplicate email, it's linux-mm@...ck.org not linux-mm@...r.kernel.org ] 
> 
> While doing some code inspection, I noticed that the slob constructor
> method can be called with a NULL pointer. If memory is tight and slob
> fails to allocate with slob_alloc() or slob_new_pages() it still calls
> the ctor() method with a NULL pointer. Looking at the first ctor()
> method I found, I noticed that it can not handle a NULL pointer (I'm
> sure others probably can't either):
> 
> static void sighand_ctor(void *data)
> {
>         struct sighand_struct *sighand = data;
> 
>         spin_lock_init(&sighand->siglock);
>         init_waitqueue_head(&sighand->signalfd_wqh);
> }
> 
> The solution is to only call the ctor() method if allocation succeeded.
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> 
> diff --git a/mm/slob.c b/mm/slob.c
> index a99fdf7..48fcb90 100644
> --- a/mm/slob.c
> +++ b/mm/slob.c
> @@ -554,7 +554,7 @@ void *kmem_cache_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
>  					    flags, node);
>  	}
>  
> -	if (c->ctor)
> +	if (b && c->ctor)
>  		c->ctor(b);
>  
>  	kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
> 
> 


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