This is a note to let you know that I've just added the patch titled
drm/msm: Avoid div-by-zero in dpu_crtc_atomic_check()
to the 5.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-msm-avoid-div-by-zero-in-dpu_crtc_atomic_check.patch
and it can be found in the queue-5.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 60b9576199cacb2135a39a887b8e3b4d62c874b5
Author: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Date: Tue Sep 1 14:59:41 2020 -0700
drm/msm: Avoid div-by-zero in dpu_crtc_atomic_check()
[ Upstream commit 22f760941844dbcee6ee446e1896532f6dff01ef ]
The cstate->num_mixers member is only set to a non-zero value once
dpu_encoder_virt_mode_set() is called, but the atomic check function can
be called by userspace before that. Let's avoid the div-by-zero here and
inside _dpu_crtc_setup_lm_bounds() by skipping this part of the atomic
check if dpu_encoder_virt_mode_set() hasn't been called yet. This fixes
an UBSAN warning:
UBSAN: Undefined behaviour in drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c:860:31
division by zero
CPU: 7 PID: 409 Comm: frecon Tainted: G S 5.4.31 #128
Hardware name: Google Trogdor (rev0) (DT)
Call trace:
dump_backtrace+0x0/0x14c
show_stack+0x20/0x2c
dump_stack+0xa0/0xd8
__ubsan_handle_divrem_overflow+0xec/0x110
dpu_crtc_atomic_check+0x97c/0x9d4
drm_atomic_helper_check_planes+0x160/0x1c8
drm_atomic_helper_check+0x54/0xbc
drm_atomic_check_only+0x6a8/0x880
drm_atomic_commit+0x20/0x5c
drm_atomic_helper_set_config+0x98/0xa0
drm_mode_setcrtc+0x308/0x5dc
drm_ioctl_kernel+0x9c/0x114
drm_ioctl+0x2ac/0x4b0
drm_compat_ioctl+0xe8/0x13c
__arm64_compat_sys_ioctl+0x184/0x324
el0_svc_common+0xa4/0x154
el0_svc_compat_handler+0x
Cc: Abhinav Kumar <abhinavk@xxxxxxxxxxxxxx>
Cc: Jeykumar Sankaran <jsanka@xxxxxxxxxxxxxx>
Cc: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
Fixes: 25fdd5933e4c ("drm/msm: Add SDM845 DPU support")
Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Reviewed-by: Abhinav Kumar <abhinavk@xxxxxxxxxxxxxx>
Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index c2729f71e2fa7..f9cb1e0da1a59 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -881,7 +881,7 @@ static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
struct drm_plane *plane;
struct drm_display_mode *mode;
- int cnt = 0, rc = 0, mixer_width, i, z_pos;
+ int cnt = 0, rc = 0, mixer_width = 0, i, z_pos;
struct dpu_multirect_plane_states multirect_plane[DPU_STAGE_MAX * 2];
int multirect_count = 0;
@@ -914,9 +914,11 @@ static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
memset(pipe_staged, 0, sizeof(pipe_staged));
- mixer_width = mode->hdisplay / cstate->num_mixers;
+ if (cstate->num_mixers) {
+ mixer_width = mode->hdisplay / cstate->num_mixers;
- _dpu_crtc_setup_lm_bounds(crtc, state);
+ _dpu_crtc_setup_lm_bounds(crtc, state);
+ }
crtc_rect.x2 = mode->hdisplay;
crtc_rect.y2 = mode->vdisplay;
