From 6419fc157e55665dc8680deb1737dc4c53c33f94 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Mon, 5 Jan 2026 23:19:26 -0700 Subject: [PATCH] drm/panic: Ensure drm_panic_type is initialized to a valid value If a user has set an invalid CONFIG_DRM_PANIC_SCREEN value (such as "qr_code" without CONFIG_DRM_PANIC_SCREEN_QR_CODE=y due to missing or incorrect Rust dependencies), there is a panic when accessing /sys/module/drm/parameters/panic_screen: [ 12.218375] BUG: unable to handle page fault for address: 0000000796dd8818 [ 12.219737] #PF: supervisor read access in kernel mode ... [ 12.227167] RIP: 0010:drm_panic_type_get+0x1b/0x30 If drm_panic_type_set() does not find a valid drm_panic_type enumeration in drm_panic_type_map based on the provided value, it does not change drm_panic_type from the default -1 value, which is not a valid index for accessing drm_panic_type_map in drm_panic_type_get(), resulting in the crash. Validate the value of CONFIG_DRM_PANIC_SCREEN at boot time via the return value of drm_panic_type_set() in drm_panic_init() and explicitly fall back to the default of "user" with a message to the user so that they can adjust their configuration or fix missing dependencies. [ 0.800697] Unsupported value for CONFIG_DRM_PANIC_SCREEN ('qr_code'), falling back to 'user'... Fixes: e85e9ccf3f84 ("drm/panic: Report invalid or unsupported panic modes") Signed-off-by: Nathan Chancellor Reviewed-by: Tvrtko Ursulin Reviewed-by: Jocelyn Falempe Signed-off-by: Tvrtko Ursulin Link: https://lore.kernel.org/r/20260105-drm_panic-handle-invalid-drm_panic_screen-v1-1-55228bd4b0f8@kernel.org --- drivers/gpu/drm/drm_panic.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c index eb7ef17b9c71..0cd574dd9d88 100644 --- a/drivers/gpu/drm/drm_panic.c +++ b/drivers/gpu/drm/drm_panic.c @@ -1072,8 +1072,11 @@ void drm_panic_unregister(struct drm_device *dev) */ void __init drm_panic_init(void) { - if (drm_panic_type == -1) - drm_panic_type_set(CONFIG_DRM_PANIC_SCREEN, NULL); + if (drm_panic_type == -1 && drm_panic_type_set(CONFIG_DRM_PANIC_SCREEN, NULL)) { + pr_warn("Unsupported value for CONFIG_DRM_PANIC_SCREEN ('%s'), falling back to 'user'...\n", + CONFIG_DRM_PANIC_SCREEN); + drm_panic_type = DRM_PANIC_TYPE_USER; + } drm_panic_qr_init(); } -- 2.47.3