Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Wed, 26 Jan 2022 16:54:43 +0100 | Subject | Re: acpi_get_devices() crash when acpi_disabled==true (was [PATCH v2] drm/privacy-screen: honor acpi=off in detect_thinkpad_privacy_screen) |
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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) >
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