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 <[email protected]>
---
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();
}
--
2.52.0
