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

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Message-ID: <Zrbm--AxRXgfHUek@gondor.apana.org.au>
Date: Sat, 10 Aug 2024 12:05:15 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Waiman Long <longman@...hat.com>
Cc: steffen.klassert@...unet.com, daniel.m.jordan@...cle.com,
	akpm@...ux-foundation.org, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, longman@...hat.com
Subject: Re: [PATCH] padata: Fix possible divide-by-0 panic in
 padata_mt_helper()

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?

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt