linux-kernel - Re: [PATCH] afs: Prefer struct_size over open coded arithmetic

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Message-ID: <20211020232620.GA1314964@embeddedor>
Date:   Wed, 20 Oct 2021 18:26:20 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Len Baker <len.baker@....com>, David Howells <dhowells@...hat.com>,
        Marc Dionne <marc.dionne@...istor.com>,
        Kees Cook <keescook@...omium.org>,
        linux-afs@...ts.infradead.org, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] afs: Prefer struct_size over open coded arithmetic

On Mon, Sep 20, 2021 at 07:09:38PM -0500, Gustavo A. R. Silva wrote:
> 
> 
> On 9/19/21 04:44, Len Baker wrote:
> > As noted in the "Deprecated Interfaces, Language Features, Attributes,
> > and Conventions" documentation [1], size calculations (especially
> > multiplication) should not be performed in memory allocator (or similar)
> > function arguments due to the risk of them overflowing. This could lead
> > to values wrapping around and a smaller allocation being made than the
> > caller was expecting. Using those allocations could lead to linear
> > overflows of heap memory and other misbehaviors.
> > 
> > So, use the struct_size() helper to do the arithmetic instead of the
> > argument "size + size * count" in the kzalloc() function.
> > 
> > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> > 
> > Signed-off-by: Len Baker <len.baker@....com>
> 
> Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

I'm taking this in my -next tree.

Thanks, Len.
--
Gustavo