On Wed, Jan 26, 2022 at 2:47 PM Hans de Goede hdegoede@redhat.com wrote:
Hi All,
On 1/23/22 10:10, Tong Zhang wrote:
when acpi=off is provided in bootarg, kernel crash with
[ 1.252739] BUG: kernel NULL pointer dereference, address: 0000000000000018 [ 1.258308] Call Trace: [ 1.258490] ? acpi_walk_namespace+0x147/0x147 [ 1.258770] acpi_get_devices+0xe4/0x137 [ 1.258921] ? drm_core_init+0xc0/0xc0 [drm] [ 1.259108] detect_thinkpad_privacy_screen+0x5e/0xa8 [drm] [ 1.259337] drm_privacy_screen_lookup_init+0xe/0xe85 [drm]
The reason is that acpi_walk_namespace expects acpi related stuff initialized but in fact it wouldn't when acpi is set to off. In this case we should honor acpi=off in detect_thinkpad_privacy_screen().
Signed-off-by: Tong Zhang ztong0001@gmail.com
Thank you for catching this and thank you for your patch. I was about to merge this, but then I realized that this might not be the best way to fix this.
A quick grep shows 10 acpi_get_devices() calls outside of drivers/acpi, and at a first glance about half of those are missing an acpi_disabled check. IMHO it would be better to simply add an acpi_disabled check to acpi_get_devices() itself.
Rafael, do you agree ?
Yes, I do.
Note the just added chrome privacy-screen check uses acpi_dev_present(), this is also used in about 10 places outside of drivers/acpi and AFAIK none of those do an acpi_disabled check.
acpi_dev_present() uses bus_find_device(&acpi_bus_type, ...) but the acpi_bus_type does not get registered when acpi_disabled is set. In the end this is fine though since bus_find_device checks for the bus not being registered and then just returns NULL.
Right.
v2: fix typo in previous commit -- my keyboard is eating letters
drivers/gpu/drm/drm_privacy_screen_x86.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/drm_privacy_screen_x86.c b/drivers/gpu/drm/drm_privacy_screen_x86.c index a2cafb294ca6..e7aa74ad0b24 100644 --- a/drivers/gpu/drm/drm_privacy_screen_x86.c +++ b/drivers/gpu/drm/drm_privacy_screen_x86.c @@ -33,6 +33,9 @@ static bool __init detect_thinkpad_privacy_screen(void) unsigned long long output; acpi_status status;
if (acpi_disabled)return false;/* Get embedded-controller handle */ status = acpi_get_devices("PNP0C09", acpi_set_handle, NULL, &ec_handle); if (ACPI_FAILURE(status) || !ec_handle)