2023-11-02 02:30:43

by Peng Hao

[permalink] [raw]

Subject: [PATCH] gpu/drm/drm_framebuffer.c: Use Macro instead of actual number.

---

Use Macro DRM_FORMAT_MAX_PLANES instead of 4, to improve modifiability.

Signed-off-by: Peng Hao <[email protected]>
---
drivers/gpu/drm/drm_framebuffer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index 2dd97473ca10..bf283dae9090 100644
--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -254,7 +254,7 @@ static int framebuffer_check(struct drm_device *dev,
}
}

- for (i = info->num_planes; i < 4; i++) {
+ for (i = info->num_planes; i < DRM_FORMAT_MAX_PLANES; i++) {
if (r->modifier[i]) {
drm_dbg_kms(dev, "non-zero modifier for unused plane %d\n", i);
return -EINVAL;
--
2.37.1

2023-11-02 06:33:25

by Dmitry Baryshkov

[permalink] [raw]

Subject: Re: [PATCH] gpu/drm/drm_framebuffer.c: Use Macro instead of actual number.

---

On Thu, 2 Nov 2023 at 04:35, Peng Hao <[email protected]> wrote:
>
> Use Macro DRM_FORMAT_MAX_PLANES instead of 4, to improve modifiability.
>
> Signed-off-by: Peng Hao <[email protected]>
> ---
> drivers/gpu/drm/drm_framebuffer.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Dmitry Baryshkov <[email protected]>


--
With best wishes
Dmitry

2023-11-02 13:28:13

by Thomas Zimmermann

[permalink] [raw]

Subject: Re: [PATCH] gpu/drm/drm_framebuffer.c: Use Macro instead of actual number.

---

Hi

Am 02.11.23 um 03:29 schrieb Peng Hao:
> Use Macro DRM_FORMAT_MAX_PLANES instead of 4, to improve modifiability.
>
> Signed-off-by: Peng Hao <[email protected]>
> ---
> drivers/gpu/drm/drm_framebuffer.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index 2dd97473ca10..bf283dae9090 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -254,7 +254,7 @@ static int framebuffer_check(struct drm_device *dev,
> }
> }
>
> - for (i = info->num_planes; i < 4; i++) {
> + for (i = info->num_planes; i < DRM_FORMAT_MAX_PLANES; i++) {

This change makes the code more fragile. '4' is a fixed constant in the
UAPI struct, while DRM_FORMAT_MAX_PLANES is an internal constant. I
agree that both should reasonably have the same value. But (potentially)
changing the value of DRM_FORMAT_MAX_PLANES will break these loops with
a possible OOB access.

To make make this code more robust, it might be better to rewrite the
tests like this

for (i = num_planes; i < ARRAY_SIZE(r->modifier); +i) {
// the test for modifier[i]
}

if (r->flags & DRM_MODE_FB_MODIFIERS) {
for (i < ARRAY_SIZE(handles)) {
// test for handles[i]
}
for (i < ARRAY_SIZE(pitches)) {
// test for pitches[i]
}
for (i < ARRAY_SIZE(offsets)) {
// test for offsets[i]
}
}

Best regards
Thomas

> if (r->modifier[i]) {
> drm_dbg_kms(dev, "non-zero modifier for unused plane %d\n", i);
> return -EINVAL;

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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