Hi,
thanks for the patch.
Am 18.01.26 um 13:50 schrieb Shenghao Yang:
Commit dc2d5ddb193e ("drm/gud: fix NULL fb and crtc dereferences
on USB disconnect") [1] only fixed the initial NULL crtc dereference
in gud_plane_atomic_update().
However, planes can also be disabled in non-hotplug paths (e.g.
display disables via the DE). The drm_dev_enter() call would not
'DE' ?
cause an early return in those and we'll subsequently oops on
dereferencing crtc:
BUG: kernel NULL pointer dereference, address: 00000000000005c8
CPU: 6 UID: 1000 PID: 3473 Comm: kwin_wayland Not tainted
6.18.2-200.vanilla.gud.fc42.x86_64 #1 PREEMPT(lazy)
RIP: 0010:gud_plane_atomic_update+0x148/0x470 [gud]
<TASK>
drm_atomic_helper_commit_planes+0x28e/0x310
drm_atomic_helper_commit_tail+0x2a/0x70
commit_tail+0xf1/0x150
drm_atomic_helper_commit+0x13c/0x180
drm_atomic_commit+0xb1/0xe0
info ? __pfx___drm_printfn_info+0x10/0x10
drm_mode_atomic_ioctl+0x70f/0x7c0
? __pfx_drm_mode_atomic_ioctl+0x10/0x10
drm_ioctl_kernel+0xae/0x100
drm_ioctl+0x2a8/0x550
? __pfx_drm_mode_atomic_ioctl+0x10/0x10
__x64_sys_ioctl+0x97/0xe0
do_syscall_64+0x7e/0x7f0
? __ct_user_enter+0x56/0xd0
? do_syscall_64+0x158/0x7f0
? __ct_user_enter+0x56/0xd0
? do_syscall_64+0x158/0x7f0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Add an early exit and disable the display controller if crtc is NULL.
It seems to me that all these calls to GUD_REQ_SET_CONTROLLER_ENABLE(^1)
and GUD_REQ_SET_DISPLAY_ENABLEshould rather go to the CRTC's
atomic_enable/atomic_disable functions. Those currently seem missing
from [1]. The atomic_update helper would then be reduced to damage
handling. Best regards Thomas [1]
https://elixir.bootlin.com/linux/v6.18.6/source/drivers/gpu/drm/gud/gud_drv.c#L341
^1: SET_CONTROLLER_ENABLE sounds like it could even be part of device
probing and runtime PM management, but that is a more invasive change.
[1] https://lore.kernel.org/all/[email protected]/
Cc: <[email protected]> # 6.18.x
Reported-by: kernel test robot <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]/
Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic
helpers")
Signed-off-by: Shenghao Yang <[email protected]>
---
drivers/gpu/drm/gud/gud_pipe.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
index 4b77be94348d..a69dee71490f 100644
--- a/drivers/gpu/drm/gud/gud_pipe.c
+++ b/drivers/gpu/drm/gud/gud_pipe.c
@@ -610,6 +610,9 @@ void gud_plane_atomic_update(struct drm_plane *plane,
if (!drm_dev_enter(drm, &idx))
return;
+ if (!crtc)
+ goto ctrl_disable;
+
if (!old_state->fb)
gud_usb_set_u8(gdrm, GUD_REQ_SET_CONTROLLER_ENABLE, 1);
@@ -633,7 +636,7 @@ void gud_plane_atomic_update(struct drm_plane *plane,
drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
ctrl_disable:
- if (!crtc->state->enable)
+ if (!crtc || !crtc->state->enable)
gud_usb_set_u8(gdrm, GUD_REQ_SET_CONTROLLER_ENABLE, 0);
drm_dev_exit(idx);
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
