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: <e752f094-adb4-4448-8bc8-e2460330eaec@redhat.com>
Date: Sat, 10 Aug 2024 21:30:25 -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 00:05, Herbert Xu wrote:
> Waiman Long <longman@...hat.com> wrote:
>> diff --git a/kernel/padata.c b/kernel/padata.c
>> index 53f4bc912712..0fa6c2895460 100644
>> --- a/kernel/padata.c
>> +++ b/kernel/padata.c
>> @@ -517,6 +517,13 @@ void __init padata_do_multithreaded(struct padata_mt_job *job)
>>         ps.chunk_size = max(ps.chunk_size, job->min_chunk);
>>         ps.chunk_size = roundup(ps.chunk_size, job->align);
>>
>> +       /*
>> +        * chunk_size can be 0 if the caller sets min_chunk to 0. So force it
>> +        * to at least 1 to prevent divide-by-0 panic in padata_mt_helper().`
>> +        */
>> +       if (!ps.chunk_size)
>> +               ps.chunk_size = 1U;
> Perhaps change the first ps.chunk_size assignment to use DIV_ROUND_UP
> instead?

I think DIV_ROUND_UP() will exactly the same problem that if chunk_size 
is 0, you still got a 0 result. round_up() only if the 2nd argument is a 
power of 2 while with DIV_ROUND_UP(), the second argument can be any 
number except 0.

Cheers,
Longman