linux-kernel - Re: [BUG -next] "random: make /dev/urandom scalable for silly userspace programs" causes crash

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Date:	Thu, 28 Jul 2016 11:12:09 -0700
From:	Joe Perches <joe@...ches.com>
To:	Theodore Ts'o <tytso@....edu>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	linux-next@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [BUG -next] "random: make /dev/urandom scalable for silly
 userspace programs" causes crash

On Wed, 2016-07-27 at 23:46 -0400, Theodore Ts'o wrote:
> On Wed, Jul 27, 2016 at 09:14:00AM +0200, Heiko Carstens wrote:
> > 
> > it looks like your patch "random: make /dev/urandom scalable for silly
> > userspace programs" within linux-next seems to be a bit broken:
> > 
> > It causes this allocation failure and subsequent crash on s390 with fake
> > NUMA enabled
> Thanks for reporting this.  This patch fixes things for you, yes?

trivia:

> diff --git a/drivers/char/random.c b/drivers/char/random.c
[]
> @@ -1668,13 +1668,12 @@ static int rand_initialize(void)
>  #ifdef CONFIG_NUMA
>  	pool = kmalloc(num_nodes * sizeof(void *),
>  		       GFP_KERNEL|__GFP_NOFAIL|__GFP_ZERO);

The __GFP_ZERO is unusual and this could use kcalloc instead.

> -	for (i=0; i < num_nodes; i++) {
> +	for_each_online_node(i) {
>  		crng = kmalloc_node(sizeof(struct crng_state),
>  				    GFP_KERNEL | __GFP_NOFAIL, i);
>  		spin_lock_init(&crng->lock);
>  		crng_initialize(crng);
>  		pool[i] = crng;
> -
>  	}
>  	mb();
>  	crng_node_pool = pool;