Re: [PATCH v1 1/5] devres: Introduce devm_kmemdup_array()

[Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>]

Hi Raag,

On Sun, Nov 24, 2024 at 01:35:23AM +0530, Raag Jadav wrote:
> Introduce '_array' variant of devm_kmemdup() for the users which lack
> multiplication overflow check.

I am not sure that this new helper is needed. Unlike allocators for
brand new objects, such as kmalloc_array(), devm_kmemdup() makes a copy
of already existing object, which is supposed to be a valid object and
therefore will have a reasonable size. So there should be no chance for
hitting this overflow unless the caller is completely confused and calls
devm_kmemdup() with random arguments (in which case all bets are off).

> 
> Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Raag Jadav <raag.jadav@xxxxxxxxx>
> ---
>  include/linux/device.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/linux/device.h b/include/linux/device.h
> index b4bde8d22697..c31f48d0dde0 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -358,6 +358,16 @@ char *devm_kstrdup(struct device *dev, const char *s, gfp_t gfp) __malloc;
>  const char *devm_kstrdup_const(struct device *dev, const char *s, gfp_t gfp);
>  void *devm_kmemdup(struct device *dev, const void *src, size_t len, gfp_t gfp)
>  	__realloc_size(3);
> +static inline void *devm_kmemdup_array(struct device *dev, const void *src,
> +				       size_t n, size_t size, gfp_t flags)
> +{
> +	size_t bytes;
> +
> +	if (unlikely(check_mul_overflow(n, size, &bytes)))
> +		return NULL;
> +
> +	return devm_kmemdup(dev, src, bytes, flags);
> +}
>  
>  unsigned long devm_get_free_pages(struct device *dev,
>  				  gfp_t gfp_mask, unsigned int order);
> -- 
> 2.35.3
> 

Thanks.

-- 
Dmitry