linux-kernel - Re: [PATCH 1/2] virtio-rng: fix boot with virtio-rng device

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Date:	Fri, 16 May 2014 11:39:35 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	mpm@...enic.com, herbert@...dor.apana.org.au,
	linux-kernel@...r.kernel.org, akong@...hat.com,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH 1/2] virtio-rng: fix boot with virtio-rng device

Sasha Levin <sasha.levin@...cle.com> writes:
> Commit "virtio-rng: support multiple virtio-rng devices" has broken
> boot with a virtio-rng device because the 'init' callback of the
> virtio-rng device was left unitialized to garbage, and got called
> by the hwrng infrastructure, killing the guest on boot.
>
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>
> Also, do we really need multiple virtio-rng devices? I know it's
> nice to have, but if there isn't a solid use-case behind it we're
> just adding bugs to working code without any benefit.

Hmm, thanks for this.  It's my fault, I should have gone through this
with a fine-tooth comb once I saw the const change in hwrng.

As Amos pointed out in the commit message, qemu support multiple entropy
sources.  It's a line ball: since you've done the work, I'll apply it
(if you'd just submitted a bug report I'd probably revert the commit).

AFAICT Amos owes you a beer :)

Cheers,
Rusty.
PS: Added Fixes: line.

>  drivers/char/hw_random/virtio-rng.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
> index 12e242b..5b25daa 100644
> --- a/drivers/char/hw_random/virtio-rng.c
> +++ b/drivers/char/hw_random/virtio-rng.c
> @@ -95,7 +95,7 @@ static int probe_common(struct virtio_device *vdev)
>  	int err, i;
>  	struct virtrng_info *vi = NULL;
>  
> -	vi = kmalloc(sizeof(struct virtrng_info), GFP_KERNEL);
> +	vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
>  	vi->hwrng.name = kmalloc(40, GFP_KERNEL);
>  	init_completion(&vi->have_data);
>  
> -- 
> 1.7.10.4
>
> --
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