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

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Message-ID: <ZrgsU-1PdxvUVMOW@gondor.apana.org.au>
Date: Sun, 11 Aug 2024 11:13:23 +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
Subject: Re: [PATCH] padata: Fix possible divide-by-0 panic in
 padata_mt_helper()

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.

Cheers,
-- 
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