linux-kernel - Re: [PATCH] drm/i915: Replace kmalloc() + copy_from_user() with memdup

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Message-ID: <5f6c7541-93ca-4b67-b4e4-33ff60e99c7d@ursulin.net>
Date: Tue, 2 Sep 2025 09:58:42 +0100
From: Tvrtko Ursulin <tursulin@...ulin.net>
To: Thorsten Blum <thorsten.blum@...ux.dev>,
 Jani Nikula <jani.nikula@...ux.intel.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Nitin Gote <nitin.r.gote@...el.com>,
 Mikołaj Wasiak <mikolaj.wasiak@...el.com>,
 Krzysztof Niemiec <krzysztof.niemiec@...el.com>,
 Andi Shyti <andi.shyti@...ux.intel.com>
Cc: Jani Nikula <jani.nikula@...el.com>, intel-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915: Replace kmalloc() + copy_from_user() with
 memdup_user()


On 02/09/2025 09:10, Thorsten Blum wrote:
> Replace kmalloc() followed by copy_from_user() with memdup_user() to
> improve and simplify set_context_image(), and to silence the following
> Coccinelle/coccicheck warning reported by memdup_user.cocci:
> 
>    WARNING opportunity for memdup_user
> 
> No functional changes intended.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> ---
> Resending this (with updated patch subject and description) because the
> CI logs [1] from my first submission [2] about a year ago are no longer
> available.
> 
> [1] https://patchwork.freedesktop.org/series/139319/
> [2] https://lore.kernel.org/lkml/20240925141750.51198-1-thorsten.blum@linux.dev/
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_context.c | 12 +++---------
>   1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 15835952352e..ed6599694835 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -2158,18 +2158,12 @@ static int set_context_image(struct i915_gem_context *ctx,
>   		goto out_ce;
>   	}
>   
> -	state = kmalloc(ce->engine->context_size, GFP_KERNEL);
> -	if (!state) {
> -		ret = -ENOMEM;
> +	state = memdup_user(u64_to_user_ptr(user.image), ce->engine->context_size);
> +	if (IS_ERR(state)) {
> +		ret = PTR_ERR(state);
>   		goto out_ce;
>   	}
>   
> -	if (copy_from_user(state, u64_to_user_ptr(user.image),
> -			   ce->engine->context_size)) {
> -		ret = -EFAULT;
> -		goto out_state;
> -	}
> -
>   	shmem_state = shmem_create_from_data(ce->engine->name,
>   					     state, ce->engine->context_size);
>   	if (IS_ERR(shmem_state)) {

LGTM.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>

Note however that CI is not picking up external patches these days, so I 
will need to re-send it for you. Once it passes I will merge it but if I 
forget feel free to ping.

Regards,

Tvrtko