linux-kernel - Re: [PATCH] drm/nouveau: Removes unnecessary args check in nouveau_uvmm_sm

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Date:   Thu, 30 Nov 2023 01:08:57 +0100
From:   Danilo Krummrich <dakr@...hat.com>
To:     Yuran Pereira <yuran.pereira@...mail.com>
Cc:     kherbst@...hat.com, lyude@...hat.com, airlied@...il.com,
        daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        nouveau@...ts.freedesktop.org
Subject: Re: [PATCH] drm/nouveau: Removes unnecessary args check in
 nouveau_uvmm_sm_prepare

On 11/16/23 21:52, Yuran Pereira wrote:
> Checking `args` after calling `op_map_prepare` is unnecessary since
> if `op_map_prepare` was to be called with  NULL args, it would lead
> to a NULL pointer dereference, thus never hitting that check.
> 
> Hence this check can be removed, and a note added to remind users of
> this function to ensure that args != NULL when calling this function
> for a map operation as it was suggested  by Danilo [1]
> 
> [1] https://lore.kernel.org/lkml/6a1ebcef-bade-45a0-9bd9-c05f0226eb88@redhat.com
> 
> Suggested-by: Danilo Krummrich <dakr@...hat.com>
> Signed-off-by: Yuran Pereira <yuran.pereira@...mail.com>

Applied to drm-misc-next.

> ---
>   drivers/gpu/drm/nouveau/nouveau_uvmm.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> index 5cf892c50f43..c8c3f1b1b604 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> @@ -604,6 +604,10 @@ op_unmap_prepare(struct drm_gpuva_op_unmap *u)
>   	drm_gpuva_unmap(u);
>   }
>   
> +/*
> + * Note: @args should not be NULL when calling for
> + * a map operation.
> + */
>   static int
>   nouveau_uvmm_sm_prepare(struct nouveau_uvmm *uvmm,
>   			struct nouveau_uvma_prealloc *new,
> @@ -624,7 +628,7 @@ nouveau_uvmm_sm_prepare(struct nouveau_uvmm *uvmm,
>   			if (ret)
>   				goto unwind;
>   
> -			if (args && vmm_get_range) {
> +			if (vmm_get_range) {
>   				ret = nouveau_uvmm_vmm_get(uvmm, vmm_get_start,
>   							   vmm_get_range);
>   				if (ret) {