2023-03-06 09:06:50

by Geert Uytterhoeven

Subject: [PATCH] drm/msm/dpu: Fix bit-shifting UB in DPU_HW_VER() macro

With gcc-5 and CONFIG_UBSAN_SHIFT=y:

drivers/gpu/drm/msm/msm_mdss.c: In function 'msm_mdss_enable':
drivers/gpu/drm/msm/msm_mdss.c:296:2: error: case label does not reduce to an integer constant
case DPU_HW_VER_800:
^
drivers/gpu/drm/msm/msm_mdss.c:299:2: error: case label does not reduce to an integer constant
case DPU_HW_VER_810:
^
drivers/gpu/drm/msm/msm_mdss.c:300:2: error: case label does not reduce to an integer constant
case DPU_HW_VER_900:
^

This happens because for major revisions 8 or greather, the non-sign bit
of the major revision number is shifted into bit 31 of a signed integer,
which is undefined behavior.

Fix this by casting the major revision number to unsigned int.

Fixes: efcd0107727c4f04 ("drm/msm/dpu: add support for SM8550")
Fixes: 4a352c2fc15aec1e ("drm/msm/dpu: Introduce SC8280XP")
Fixes: 100d7ef6995d1f86 ("drm/msm/dpu: add support for SM8450")
Signed-off-by: Geert Uytterhoeven <[email protected]>
---
drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
index ddab9caebb18c40d..bbd3cbdd77956c5d 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
@@ -19,8 +19,9 @@
*/
#define MAX_BLOCKS 12

-#define DPU_HW_VER(MAJOR, MINOR, STEP) (((MAJOR & 0xF) << 28) |\
- ((MINOR & 0xFFF) << 16) |\
+#define DPU_HW_VER(MAJOR, MINOR, STEP) \
+ ((((unsigned int)MAJOR & 0xF) << 28) | \
+ ((MINOR & 0xFFF) << 16) | \
(STEP & 0xFFFF))

#define DPU_HW_MAJOR(rev) ((rev) >> 28)
--
2.34.1

2023-03-21 15:09:11

by Randy Dunlap

Subject: Re: [PATCH] drm/msm/dpu: Fix bit-shifting UB in DPU_HW_VER() macro

On 3/6/23 01:06, Geert Uytterhoeven wrote:
> With gcc-5 and CONFIG_UBSAN_SHIFT=y:
>
> drivers/gpu/drm/msm/msm_mdss.c: In function 'msm_mdss_enable':
> drivers/gpu/drm/msm/msm_mdss.c:296:2: error: case label does not reduce to an integer constant
> case DPU_HW_VER_800:
> ^
> drivers/gpu/drm/msm/msm_mdss.c:299:2: error: case label does not reduce to an integer constant
> case DPU_HW_VER_810:
> ^
> drivers/gpu/drm/msm/msm_mdss.c:300:2: error: case label does not reduce to an integer constant
> case DPU_HW_VER_900:
> ^
>
> This happens because for major revisions 8 or greather, the non-sign bit
> of the major revision number is shifted into bit 31 of a signed integer,
> which is undefined behavior.
>
> Fix this by casting the major revision number to unsigned int.
>
> Fixes: efcd0107727c4f04 ("drm/msm/dpu: add support for SM8550")
> Fixes: 4a352c2fc15aec1e ("drm/msm/dpu: Introduce SC8280XP")
> Fixes: 100d7ef6995d1f86 ("drm/msm/dpu: add support for SM8450")
> Signed-off-by: Geert Uytterhoeven <[email protected]>

Reviewed-by: Randy Dunlap <[email protected]>

Thanks.

> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> index ddab9caebb18c40d..bbd3cbdd77956c5d 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> @@ -19,8 +19,9 @@
> */
> #define MAX_BLOCKS 12
>
> -#define DPU_HW_VER(MAJOR, MINOR, STEP) (((MAJOR & 0xF) << 28) |\
> - ((MINOR & 0xFFF) << 16) |\
> +#define DPU_HW_VER(MAJOR, MINOR, STEP) \
> + ((((unsigned int)MAJOR & 0xF) << 28) | \
> + ((MINOR & 0xFFF) << 16) | \
> (STEP & 0xFFFF))
>
> #define DPU_HW_MAJOR(rev) ((rev) >> 28)

--
~Randy

2023-03-22 20:52:58

by Rob Clark

Subject: Re: [PATCH] drm/msm/dpu: Fix bit-shifting UB in DPU_HW_VER() macro

On Tue, Mar 21, 2023 at 8:08 AM Randy Dunlap <[email protected]> wrote:
>
>
>
> On 3/6/23 01:06, Geert Uytterhoeven wrote:
> > With gcc-5 and CONFIG_UBSAN_SHIFT=y:
> >
> > drivers/gpu/drm/msm/msm_mdss.c: In function 'msm_mdss_enable':
> > drivers/gpu/drm/msm/msm_mdss.c:296:2: error: case label does not reduce to an integer constant
> > case DPU_HW_VER_800:
> > ^
> > drivers/gpu/drm/msm/msm_mdss.c:299:2: error: case label does not reduce to an integer constant
> > case DPU_HW_VER_810:
> > ^
> > drivers/gpu/drm/msm/msm_mdss.c:300:2: error: case label does not reduce to an integer constant
> > case DPU_HW_VER_900:
> > ^
> >
> > This happens because for major revisions 8 or greather, the non-sign bit
> > of the major revision number is shifted into bit 31 of a signed integer,
> > which is undefined behavior.
> >
> > Fix this by casting the major revision number to unsigned int.
> >
> > Fixes: efcd0107727c4f04 ("drm/msm/dpu: add support for SM8550")
> > Fixes: 4a352c2fc15aec1e ("drm/msm/dpu: Introduce SC8280XP")
> > Fixes: 100d7ef6995d1f86 ("drm/msm/dpu: add support for SM8450")
> > Signed-off-by: Geert Uytterhoeven <[email protected]>
>
> Reviewed-by: Randy Dunlap <[email protected]>

Reviewed-by: Rob Clark <[email protected]>

>
> Thanks.
>
> > ---
> > drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> > index ddab9caebb18c40d..bbd3cbdd77956c5d 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> > @@ -19,8 +19,9 @@
> > */
> > #define MAX_BLOCKS 12
> >
> > -#define DPU_HW_VER(MAJOR, MINOR, STEP) (((MAJOR & 0xF) << 28) |\
> > - ((MINOR & 0xFFF) << 16) |\
> > +#define DPU_HW_VER(MAJOR, MINOR, STEP) \
> > + ((((unsigned int)MAJOR & 0xF) << 28) | \
> > + ((MINOR & 0xFFF) << 16) | \
> > (STEP & 0xFFFF))
> >
> > #define DPU_HW_MAJOR(rev) ((rev) >> 28)
>
> --
> ~Randy

2023-03-28 22:40:35

by Dmitry Baryshkov

Subject: Re: [PATCH] drm/msm/dpu: Fix bit-shifting UB in DPU_HW_VER() macro

On Mon, 06 Mar 2023 10:06:33 +0100, Geert Uytterhoeven wrote:
> With gcc-5 and CONFIG_UBSAN_SHIFT=y:
>
> drivers/gpu/drm/msm/msm_mdss.c: In function 'msm_mdss_enable':
> drivers/gpu/drm/msm/msm_mdss.c:296:2: error: case label does not reduce to an integer constant
> case DPU_HW_VER_800:
> ^
> drivers/gpu/drm/msm/msm_mdss.c:299:2: error: case label does not reduce to an integer constant
> case DPU_HW_VER_810:
> ^
> drivers/gpu/drm/msm/msm_mdss.c:300:2: error: case label does not reduce to an integer constant
> case DPU_HW_VER_900:
> ^
>
> [...]

Applied, thanks!

[1/1] drm/msm/dpu: Fix bit-shifting UB in DPU_HW_VER() macro
https://gitlab.freedesktop.org/lumag/msm/-/commit/c8f370bde5b9

Best regards,
--
Dmitry Baryshkov <[email protected]>