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

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Date: Mon, 03 Jun 2024 14:03:34 +0200
From: Andreas Hindborg <nmi@...aspace.dk>
To: John Garry <john.g.garry@...cle.com>
Cc: Jens Axboe <axboe@...nel.dk>,  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

John Garry <john.g.garry@...cle.com> writes:

> 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?

Right 👍

>
>  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

Cool, I will use that instead.


BR Andreas