* [PATCH] drm/amd/display: Fix division by zero in setup_dsc_config
@ 2024-04-10 4:34 Jose Fernandez
2024-04-22 15:38 ` Markus Elfring
0 siblings, 1 reply; 2+ messages in thread
From: Jose Fernandez @ 2024-04-10 4:34 UTC (permalink / raw
To: Harry Wentland, Leo Li, Rodrigo Siqueira, Alex Deucher,
christian.koenig, Xinhui.Pan, David Airlie, Daniel Vetter,
Wenjing Liu, Alan Liu, George Shen, Nicholas Kazlauskas,
Ilya Bakoulin, Nasir Osman, Hamza Mahfooz, Fangzhi Zuo, Leo Ma,
amd-gfx, dri-devel
Cc: linux-kernel, Jose Fernandez
When slice_height is 0, the division by slice_height in the calculation
of the number of slices will cause a division by zero driver crash. This
leaves the kernel in a state that requires a reboot. This patch adds a
check to avoid the division by zero.
The stack trace below is for the 6.8.4 Kernel. I reproduced the issue on
a Z16 Gen 2 Lenovo Thinkpad with a Apple Studio Display monitor
connected via Thunderbolt. The amdgpu driver crashed with this exception
when I rebooted the system with the monitor connected.
kernel: ? die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434 arch/x86/kernel/dumpstack.c:447)
kernel: ? do_trap (arch/x86/kernel/traps.c:113 arch/x86/kernel/traps.c:154)
kernel: ? setup_dsc_config (drivers/gpu/drm/amd/amdgpu/../display/dc/dsc/dc_dsc.c:1053) amdgpu
kernel: ? do_error_trap (./arch/x86/include/asm/traps.h:58 arch/x86/kernel/traps.c:175)
kernel: ? setup_dsc_config (drivers/gpu/drm/amd/amdgpu/../display/dc/dsc/dc_dsc.c:1053) amdgpu
kernel: ? exc_divide_error (arch/x86/kernel/traps.c:194 (discriminator 2))
kernel: ? setup_dsc_config (drivers/gpu/drm/amd/amdgpu/../display/dc/dsc/dc_dsc.c:1053) amdgpu
kernel: ? asm_exc_divide_error (./arch/x86/include/asm/idtentry.h:548)
kernel: ? setup_dsc_config (drivers/gpu/drm/amd/amdgpu/../display/dc/dsc/dc_dsc.c:1053) amdgpu
kernel: dc_dsc_compute_config (drivers/gpu/drm/amd/amdgpu/../display/dc/dsc/dc_dsc.c:1109) amdgpu
After applying this patch, the driver no longer crashes when the monitor
is connected and the system is rebooted. I believe this is the same
issue reported for 3113.
Signed-off-by: Jose Fernandez <josef@netflix.com>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3113
---
drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
index ac41f9c0a283..597d5425d6cb 100644
--- a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
+++ b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
@@ -1055,7 +1055,12 @@ static bool setup_dsc_config(
if (!is_dsc_possible)
goto done;
- dsc_cfg->num_slices_v = pic_height/slice_height;
+ if (slice_height > 0)
+ dsc_cfg->num_slices_v = pic_height/slice_height;
+ else {
+ is_dsc_possible = false;
+ goto done;
+ }
if (target_bandwidth_kbps > 0) {
is_dsc_possible = decide_dsc_target_bpp_x16(
--
2.44.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] drm/amd/display: Fix division by zero in setup_dsc_config
2024-04-10 4:34 [PATCH] drm/amd/display: Fix division by zero in setup_dsc_config Jose Fernandez
@ 2024-04-22 15:38 ` Markus Elfring
0 siblings, 0 replies; 2+ messages in thread
From: Markus Elfring @ 2024-04-22 15:38 UTC (permalink / raw
To: Jose Fernandez, amd-gfx, dri-devel, kernel-janitors, Alan Liu,
Alex Deucher, Christian König, Daniel Vetter, David Airlie,
Fangzhi Zuo, George Shen, Hamza Mahfooz, Harry Wentland,
Ilya Bakoulin, Leo Li, Leo Ma, Nasir Osman, Nicholas Kazlauskas,
Rodrigo Siqueira, Wenjing Liu, Xinhui Pan
Cc: LKML
…
> +++ b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
> @@ -1055,7 +1055,12 @@ static bool setup_dsc_config(
> if (!is_dsc_possible)
> goto done;
>
> - dsc_cfg->num_slices_v = pic_height/slice_height;
> + if (slice_height > 0)
> + dsc_cfg->num_slices_v = pic_height/slice_height;
> + else {
> + is_dsc_possible = false;
> + goto done;
> + }
>
> if (target_bandwidth_kbps > 0) {
> is_dsc_possible = decide_dsc_target_bpp_x16(
I suggest to take another coding style concern into account.
Please use curly brackets for both if branches.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?h=v6.9-rc5#n213
Regards,
Markus
^ permalink raw reply [flat|nested] 2+ messages in thread
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