linux-kernel - Re: [PATCH] padata: Fix possible divide-by-0 panic in padata_mt

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <88c188dc-3664-45db-b54a-11feca59d7d2@redhat.com>
Date: Sat, 10 Aug 2024 23:27:55 -0400
From: Waiman Long <longman@...hat.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: steffen.klassert@...unet.com, daniel.m.jordan@...cle.com,
 akpm@...ux-foundation.org, linux-crypto@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] padata: Fix possible divide-by-0 panic in
 padata_mt_helper()


On 8/10/24 23:13, Herbert Xu wrote:
> On Sat, Aug 10, 2024 at 11:11:07PM -0400, Waiman Long wrote:
>>> Unless I'm missing something chunk_size cannot be zero before the
>>> division because that's the first thing we check upon entry into
>>> this function.
>> chunk_size is initialized as
>>
>> ps.chunk_size = job->size / (ps.nworks * load_balance_factor);
>>
>> chunk_size will be 0 if job->size < (ps.nworks * load_balance_factor). If
>> min_chunk is 0, chunk_size will remain 0.
> That's why I was suggesting that you replace the division by
> DIV_ROUND_UP.  That should ensure that ps.chunk_size is not zero.

Now I see what you mean. Yes, we can probably change that to a 
DIV_ROUND_UP operation to make sure that chunk_size is at least one 
unless job->size is 0. I still think the current patch is a bit more 
fail-safe.

Cheers, Longman