Re: [PATCH] drm/panthor: fix firmware control interface bounds checks

[Liviu Dudau <liviu.dudau@arm.com>]

On Mon, Jul 20, 2026 at 03:44:35PM +0200, Osama Abdelkader wrote:
> panthor_init_cs_iface() and panthor_init_csg_iface() validate firmware
> control interface offsets with 32-bit arithmetic and the size of the host
> wrapper structures. The offsets are derived from firmware-provided strides,
> so the arithmetic can wrap before the bounds check, and the host wrapper
> size is not the size of the firmware control interface being mapped.

How can the offsets wrap with the firmware-provided strides? It's not like
the firmware provides arbitrarily large strides.

> 
> Use 64-bit arithmetic for the computed offsets and validate against the
> actual firmware control interface structure sizes with subtraction-based
> bounds checks. Also validate that the shared section is large enough for
> the global control interface before using it.
> 
> Fixes: 2718d91816ee ("drm/panthor: Add the FW logical block")
> Cc: stable@vger.kernel.org
> Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
> ---
>  drivers/gpu/drm/panthor/panthor_fw.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> index eee2bc7e8541..e2fcbd639c3c 100644
> --- a/drivers/gpu/drm/panthor/panthor_fw.c
> +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> @@ -897,15 +897,16 @@ static int panthor_init_cs_iface(struct panthor_device *ptdev,
>  	struct panthor_fw_csg_iface *csg_iface = panthor_fw_get_csg_iface(ptdev, csg_idx);
>  	struct panthor_fw_cs_iface *cs_iface = &ptdev->fw->iface.streams[csg_idx][cs_idx];
>  	u64 shared_section_sz = panthor_kernel_bo_size(ptdev->fw->shared_section->mem);
> -	u32 iface_offset = CSF_GROUP_CONTROL_OFFSET +
> -			   (csg_idx * glb_iface->control->group_stride) +
> +	u64 iface_offset = CSF_GROUP_CONTROL_OFFSET +
> +			   ((u64)csg_idx * glb_iface->control->group_stride) +
>  			   CSF_STREAM_CONTROL_OFFSET +
> -			   (cs_idx * csg_iface->control->stream_stride);
> +			   ((u64)cs_idx * csg_iface->control->stream_stride);
>  	struct panthor_fw_cs_iface *first_cs_iface =
>  		panthor_fw_get_cs_iface(ptdev, 0, 0);
>  
> -	if (iface_offset + sizeof(*cs_iface) >= shared_section_sz)
> +	if (iface_offset > shared_section_sz ||
> +	    sizeof(*cs_iface->control) > shared_section_sz - iface_offset)
>  		return -EINVAL;
>  
>  	spin_lock_init(&cs_iface->lock);
>  	cs_iface->control = ptdev->fw->shared_section->mem->kmap + iface_offset;
> @@ -955,11 +956,13 @@ static int panthor_init_csg_iface(struct panthor_device *ptdev,
>  	struct panthor_fw_global_iface *glb_iface = panthor_fw_get_glb_iface(ptdev);
>  	struct panthor_fw_csg_iface *csg_iface = &ptdev->fw->iface.groups[csg_idx];
>  	u64 shared_section_sz = panthor_kernel_bo_size(ptdev->fw->shared_section->mem);
> -	u32 iface_offset = CSF_GROUP_CONTROL_OFFSET + (csg_idx * glb_iface->control->group_stride);
> +	u64 iface_offset = CSF_GROUP_CONTROL_OFFSET +
> +			   ((u64)csg_idx * glb_iface->control->group_stride);
>  	unsigned int i;
>  
> -	if (iface_offset + sizeof(*csg_iface) >= shared_section_sz)
> +	if (iface_offset > shared_section_sz ||
> +	    sizeof(*csg_iface->control) > shared_section_sz - iface_offset)
>  		return -EINVAL;
>  
>  	spin_lock_init(&csg_iface->lock);
>  	csg_iface->control = ptdev->fw->shared_section->mem->kmap + iface_offset;
> @@ -1011,12 +1014,16 @@ static u32 panthor_get_instr_features(struct panthor_device *ptdev)
>  static int panthor_fw_init_ifaces(struct panthor_device *ptdev)
>  {
>  	struct panthor_fw_global_iface *glb_iface = &ptdev->fw->iface.global;
> +	u64 shared_section_sz = panthor_kernel_bo_size(ptdev->fw->shared_section->mem);
>  	unsigned int i;
>  
>  	if (!ptdev->fw->shared_section->mem->kmap)
>  		return -EINVAL;
>  
> +	if (sizeof(*glb_iface->control) > shared_section_sz)
> +		return -EINVAL;
> +
>  	spin_lock_init(&glb_iface->lock);
>  	glb_iface->control = ptdev->fw->shared_section->mem->kmap;
>  
>  	if (!glb_iface->control->version) {
> -- 
> 2.43.0
> 

I'm OK with the general content of the patch, so:

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu


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