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Sun, 18 Jan 2026 04:51:02 -0800 (PST) From: Shenghao Yang To: Ruben Wauters , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Shenghao Yang , stable@vger.kernel.org, kernel test robot , Dan Carpenter Subject: [PATCH] drm/gud: fix NULL crtc dereference on display disable Date: Sun, 18 Jan 2026 20:50:44 +0800 Message-ID: <20260118125044.54467-1-me@shenghaoyang.info> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 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.vanill= a.gud.fc42.x86_64 #1 PREEMPT(lazy) RIP: 0010:gud_plane_atomic_update+0x148/0x470 [gud] 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. [1] https://lore.kernel.org/all/20251231055039.44266-1-me@shenghaoyang.info/ Cc: # 6.18.x Reported-by: kernel test robot Reported-by: Dan Carpenter Closes: https://lore.kernel.org/r/202601142159.0v8ilfVs-lkp@intel.com/ Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic = helpers") Signed-off-by: Shenghao Yang --- 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; =20 + if (!crtc) + goto ctrl_disable; + if (!old_state->fb) gud_usb_set_u8(gdrm, GUD_REQ_SET_CONTROLLER_ENABLE, 1); =20 @@ -633,7 +636,7 @@ void gud_plane_atomic_update(struct drm_plane *plane, drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE); =20 ctrl_disable: - if (!crtc->state->enable) + if (!crtc || !crtc->state->enable) gud_usb_set_u8(gdrm, GUD_REQ_SET_CONTROLLER_ENABLE, 0); =20 drm_dev_exit(idx); --=20 2.52.0