linux-hardening - Re: [PATCH] afs: Prefer struct

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Message-ID: <4028805.1635846297@warthog.procyon.org.uk>
Date:   Tue, 02 Nov 2021 09:44:57 +0000
From:   David Howells <dhowells@...hat.com>
To:     Len Baker <len.baker@....com>
Cc:     dhowells@...hat.com, Marc Dionne <marc.dionne@...istor.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        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

Len Baker <len.baker@....com> 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>

Acked-by: David Howells <dhowells@...hat.com>