linux-hardening - Re: [PATCH] RDMA/bnxt_re: Prefer kcalloc over open coded arithmetic

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Date:   Wed, 8 Sep 2021 08:44:40 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Len Baker <len.baker@....com>
Cc:     Selvin Xavier <selvin.xavier@...adcom.com>,
        Naresh Kumar PBS <nareshkumar.pbs@...adcom.com>,
        Doug Ledford <dledford@...hat.com>,
        Kees Cook <keescook@...omium.org>, linux-rdma@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RDMA/bnxt_re: Prefer kcalloc over open coded arithmetic

On Sun, Sep 05, 2021 at 10:18:12AM +0200, 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.
> 
> In this case this is not actually dynamic sizes: both sides of the
> multiplication are constant values. However it is best to refactor this
> anyway, just to keep the open-coded math idiom out of code.
> 
> So, use the purpose specific kcalloc() function instead of the argument
> size * count in the kzalloc() function.
> 
> Also, remove the unnecessary initialization of the sqp_tbl variable
> since it is set a few lines later.
> 
> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> 
> Signed-off-by: Len Baker <len.baker@....com>
> Reviewed-by: Leon Romanovsky <leonro@...dia.com>
> Acked-by: Selvin Xavier <selvin.xavier@...adcom.com>
> ---
>  drivers/infiniband/hw/bnxt_re/ib_verbs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Applied to for-rc, thanks

Jason