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From: Andreas Hindborg <nmi@metaspace.dk>
To: John Garry <john.g.garry@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>,  Andreas Hindborg
 <a.hindborg@samsung.com>,  Keith Busch <kbusch@kernel.org>,
  linux-block@vger.kernel.org,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH] null_blk: fix validation of block size
In-Reply-To: <d6999fef-aadf-494e-ad58-f27dfd975535@oracle.com> (John Garry's
	message of "Sun, 2 Jun 2024 11:57:03 +0100")
References: <20240601202351.691952-1-nmi@metaspace.dk>
	<d6999fef-aadf-494e-ad58-f27dfd975535@oracle.com>
Date: Mon, 03 Jun 2024 14:03:34 +0200
Message-ID: <87frtumdwp.fsf@metaspace.dk>
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John Garry <john.g.garry@oracle.com> writes:

> On 01/06/2024 21:23, Andreas Hindborg wrote:
>> From: Andreas Hindborg <a.hindborg@samsung.com>
>> Block size should be between 512
>
>
>>and 4096
>
> Or PAGE_SIZE?

Right =F0=9F=91=8D

>
>  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=3D1536 [1].
>> Link:
>> https://urldefense.com/v3/__https://lore.kernel.org/all/87wmn8mocd.fsf@m=
etaspace.dk/__;!!ACWV5N9M2RV99hQ!OWXI3DGxeIAWvKfM5oVSiA5fTWmiRvUctIdVrcBcKn=
O_HF-vgkarVfd27jkvQ1-JjNgX5IFIvBWcsUttvg$
>> Signed-off-by: Andreas Hindborg <a.hindborg@samsung.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 =3D NULL_Q_MQ;
>>   	}
>>   -	dev->blocksize =3D round_down(dev->blocksize, 512);
>> -	dev->blocksize =3D clamp_t(unsigned int, dev->blocksize, 512, 4096);
>> +	if ((dev->blocksize < 512 || dev->blocksize > 4096) ||
>> +	    ((dev->blocksize & (dev->blocksize - 1)) !=3D 0)) {
>> +		return -EINVAL;
>> +	}
>
> Looks like blk_validate_block_size(), modulo PAGE_SIZE check

Cool, I will use that instead.


BR Andreas