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Subject: Re: [PATCH 1/8] mm: slab: provide krealloc_array()
To:     Bartosz Golaszewski <brgl@bgdev.pl>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        Gustavo Padovan <gustavo@padovan.org>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Tony Luck <tony.luck@intel.com>,
        James Morse <james.morse@arm.com>,
        Robert Richter <rric@kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>
Cc:     linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org,
        linux-edac@vger.kernel.org, linux-gpio@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, linux-mm@kvack.org,
        alsa-devel@alsa-project.org,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
References: <20201027121725.24660-1-brgl@bgdev.pl>
 <20201027121725.24660-2-brgl@bgdev.pl>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <21ae795b-c0f4-bbf3-20f6-830d0980a673@suse.cz>
Date:   Tue, 27 Oct 2020 19:20:06 +0100
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On 10/27/20 1:17 PM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> 
> When allocating an array of elements, users should check for
> multiplication overflow or preferably use one of the provided helpers
> like: kmalloc_array().
> 
> There's no krealloc_array() counterpart but there are many users who use
> regular krealloc() to reallocate arrays. Let's provide an actual
> krealloc_array() implementation.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Makes sense.
Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>   include/linux/slab.h | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index dd6897f62010..0e6683affee7 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -592,6 +592,17 @@ static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
>   	return __kmalloc(bytes, flags);
>   }
>   
> +static __must_check inline void *
> +krealloc_array(void *p, size_t new_n, size_t new_size, gfp_t flags)
> +{
> +	size_t bytes;
> +
> +	if (unlikely(check_mul_overflow(new_n, new_size, &bytes)))
> +		return NULL;
> +
> +	return krealloc(p, bytes, flags);
> +}
> +
>   /**
>    * kcalloc - allocate memory for an array. The memory is set to zero.
>    * @n: number of elements.
>