From: Hans de Goede <hdegoede@redhat.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Tong Zhang <ztong0001@gmail.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
dri-devel <dri-devel@lists.freedesktop.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
linux-acpi <linux-acpi@vger.kernel.org>
Subject: Re: acpi_get_devices() crash when acpi_disabled==true (was [PATCH v2] drm/privacy-screen: honor acpi=off in detect_thinkpad_privacy_screen)
Date: Thu, 27 Jan 2022 14:05:30 +0100 [thread overview]
Message-ID: <994f94b2-61d3-1754-d733-732a0fb47d50@redhat.com> (raw)
In-Reply-To: <CAJZ5v0hJWW_vZ3wwajE7xT38aWjY7cZyvqMJpXHzUL98-SiCVQ@mail.gmail.com>
Hi,
On 1/26/22 18:11, Rafael J. Wysocki wrote:
> On Wed, Jan 26, 2022 at 5:41 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Hi,
>>
>> On 1/26/22 16:54, Rafael J. Wysocki wrote:
>>> 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.
>>
>> Did you see my follow-up that that is not going to work because
>> acpi_get_devices() is an acpica function ?
>
> No, I didn't, but it is possible to add a wrapper doing the check
> around it and convert all of the users.
Yes I did think about that. Note that I've gone ahead and pushed
the fix which started this to drm-misc-fixes, to resolve the crash
for now.
If we add such a wrapper we can remove a bunch of acpi_disabled checks
from various callers.
> Alternatively, the ACPICA function can check acpi_gbl_root_node
> against NULL, like in the attached (untested) patch.
That is probably an even better idea, as that avoids the need
for a wrapper altogether. So I believe that that is the best
solution.
Regards,
Hans
next prev parent reply other threads:[~2022-01-27 13:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220123091004.763775-1-ztong0001@gmail.com>
2022-01-26 13:47 ` acpi_get_devices() crash when acpi_disabled==true (was [PATCH v2] drm/privacy-screen: honor acpi=off in detect_thinkpad_privacy_screen) Hans de Goede
2022-01-26 14:25 ` Hans de Goede
2022-01-26 15:54 ` Rafael J. Wysocki
2022-01-26 16:41 ` Hans de Goede
2022-01-26 17:11 ` Rafael J. Wysocki
2022-01-27 13:05 ` Hans de Goede [this message]
2022-01-27 13:33 ` Rafael J. Wysocki
2022-01-27 13:39 ` Hans de Goede
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