linux-hardening - Re: [PATCH] i3c/master/mipi-i3c-hci: Prefer struct

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Message-ID: <65q16p1-7o22-pq77-38s8-9rr27p56s16n@onlyvoer.pbz>
Date:   Mon, 6 Sep 2021 00:30:16 -0400 (EDT)
From:   Nicolas Pitre <npitre@...libre.com>
To:     Len Baker <len.baker@....com>
cc:     Boris Brezillon <boris.brezillon@...labora.com>,
        Kees Cook <keescook@...omium.org>,
        linux-i3c@...ts.infradead.org, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i3c/master/mipi-i3c-hci: Prefer struct_size over open
 coded arithmetic

On Sun, 5 Sep 2021, 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 + count * size" in the kzalloc() function.
> 
> [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>

Acked-by: Nicolas Pitre <npitre@...libre.com>


> ---
>  drivers/i3c/master/mipi-i3c-hci/dma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
> index af873a9be050..2990ac9eaade 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/dma.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
> @@ -223,7 +223,7 @@ static int hci_dma_init(struct i3c_hci *hci)
>  	}
>  	if (nr_rings > XFER_RINGS)
>  		nr_rings = XFER_RINGS;
> -	rings = kzalloc(sizeof(*rings) + nr_rings * sizeof(*rh), GFP_KERNEL);
> +	rings = kzalloc(struct_size(rings, headers, nr_rings), GFP_KERNEL);
>  	if (!rings)
>  		return -ENOMEM;
>  	hci->io_data = rings;
> --
> 2.25.1
> 
>