linux-kernel - Re: [PATCH] null_blk: fix validation of block size

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Date: Sun, 2 Jun 2024 11:57:03 +0100
From: John Garry <john.g.garry@...cle.com>
To: Andreas Hindborg <nmi@...aspace.dk>, Jens Axboe <axboe@...nel.dk>
Cc: Andreas Hindborg <a.hindborg@...sung.com>,
        Keith Busch
 <kbusch@...nel.org>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] null_blk: fix validation of block size

On 01/06/2024 21:23, Andreas Hindborg wrote:
> From: Andreas Hindborg <a.hindborg@...sung.com>
> 
> Block size should be between 512


>and 4096

Or PAGE_SIZE?

  and be a power of 2. The current
> check does not validate this, so update the check.
> 
> Without this patch, null_blk would Oops due to a null pointer deref when
> loaded with bs=1536 [1].
> 
> Link: https://urldefense.com/v3/__https://lore.kernel.org/all/87wmn8mocd.fsf@metaspace.dk/__;!!ACWV5N9M2RV99hQ!OWXI3DGxeIAWvKfM5oVSiA5fTWmiRvUctIdVrcBcKnO_HF-vgkarVfd27jkvQ1-JjNgX5IFIvBWcsUttvg$
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
> ---
>   drivers/block/null_blk/main.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index eb023d267369..6a26888c52bb 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -1823,8 +1823,10 @@ static int null_validate_conf(struct nullb_device *dev)
>   		dev->queue_mode = NULL_Q_MQ;
>   	}
>   
> -	dev->blocksize = round_down(dev->blocksize, 512);
> -	dev->blocksize = clamp_t(unsigned int, dev->blocksize, 512, 4096);
> +	if ((dev->blocksize < 512 || dev->blocksize > 4096) ||
> +	    ((dev->blocksize & (dev->blocksize - 1)) != 0)) {
> +		return -EINVAL;
> +	}

Looks like blk_validate_block_size(), modulo PAGE_SIZE check

>   
>   	if (dev->use_per_node_hctx) {
>   		if (dev->submit_queues != nr_online_nodes)
> 
> base-commit: 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0