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7149be786d
gud_plane_atomic_update() currently handles both crtc state and framebuffer updates - the complexity has led to a few accidental NULL pointer dereferences. Commitdc2d5ddb19("drm/gud: fix NULL fb and crtc dereferences on USB disconnect") [1] fixed an earlier dereference but planes can also be disabled in non-hotplug paths (e.g. display disables via the desktop environment). The drm_dev_enter() call would not cause an early return in those and 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 Split out crtc handling from gud_plane_atomic_update() into atomic_enable() and atomic_disable() functions to delegate crtc state transitioning work to the DRM helpers. To preserve the gud state commit sequence [2], switch to the runtime PM version of drm_atomic_helper_commit_tail() which ensures that crtcs are enabled (hence sending the GUD_REQ_SET_CONTROLLER_ENABLE and GUD_REQ_SET_DISPLAY_ENABLE requests) before a framebuffer update is sent. [1] https://lore.kernel.org/all/20251231055039.44266-1-me@shenghaoyang.info/ [2] https://github.com/notro/gud/wiki/GUD-Protocol#display-state Reported-by: kernel test robot <lkp@intel.com> Reported-by: Dan Carpenter <dan.carpenter@linaro.org> Closes: https://lore.kernel.org/r/202601142159.0v8ilfVs-lkp@intel.com/ Fixes:73cfd166e0("drm/gud: Replace simple display pipe with DRM atomic helpers") Cc: <stable@vger.kernel.org> # 6.19.x Cc: <stable@vger.kernel.org> # 6.18.x Signed-off-by: Shenghao Yang <me@shenghaoyang.info> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> Acked-by: Ruben Wauters <rubenru09@aol.com> Signed-off-by: Ruben Wauters <rubenru09@aol.com> Link: https://patch.msgid.link/20260222054551.80864-1-me@shenghaoyang.info