linux-hardening - Re: [PATCH][next] comedi: das16: Use struct_size() helper in comedi_alloc

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Message-ID: <43b079ef-1c4a-b4c4-62b3-10d6a62a3bac@mev.co.uk>
Date:   Wed, 26 Jan 2022 12:19:42 +0000
From:   Ian Abbott <abbotti@....co.uk>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>
Cc:     linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] comedi: das16: Use struct_size() helper in
 comedi_alloc_spriv()

On 25/01/2022 23:25, Gustavo A. R. Silva wrote:
> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worst scenario, could lead to heap overflows.
> 
> Also, address the following sparse warnings:
> drivers/comedi/drivers/das16.c:964:45: warning: using sizeof on a flexible structure
> drivers/comedi/drivers/das16.c:998:45: warning: using sizeof on a flexible structure
> 
> Link: https://github.com/KSPP/linux/issues/174
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>   drivers/comedi/drivers/das16.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/comedi/drivers/das16.c b/drivers/comedi/drivers/das16.c
> index 937a69ce0977..728dc02156c8 100644
> --- a/drivers/comedi/drivers/das16.c
> +++ b/drivers/comedi/drivers/das16.c
> @@ -961,7 +961,7 @@ static const struct comedi_lrange *das16_ai_range(struct comedi_device *dev,
>   
>   		/* allocate single-range range table */
>   		lrange = comedi_alloc_spriv(s,
> -					    sizeof(*lrange) + sizeof(*krange));
> +					    struct_size(lrange, range, 1));
>   		if (!lrange)
>   			return &range_unknown;
>   
> @@ -995,7 +995,7 @@ static const struct comedi_lrange *das16_ao_range(struct comedi_device *dev,
>   
>   		/* allocate single-range range table */
>   		lrange = comedi_alloc_spriv(s,
> -					    sizeof(*lrange) + sizeof(*krange));
> +					    struct_size(lrange, range, 1));
>   		if (!lrange)
>   			return &range_unknown;
>   

Looks like a nice tidy-up, thanks!

Reviewed-by: Ian Abbott <abbotti@....co.uk>

(Note, I do not have anywhere to commit it, personally.)

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