* [PATCH] fbdev: Fix unregistering of framebuffers without device
@ 2022-04-04 19:44 Thomas Zimmermann
2022-04-05 9:01 ` Daniel Vetter
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Thomas Zimmermann @ 2022-04-04 19:44 UTC (permalink / raw)
To: daniel, deller, sudipm.mukherjee, sam, javierm, zackr, hdegoede
Cc: linux-fbdev, dri-devel, Thomas Zimmermann, stable, Daniel Vetter,
Zheyu Ma, Xiyu Yang, Zhen Lei, Matthew Wilcox, Alex Deucher,
Tetsuo Handa, Guenter Roeck
OF framebuffers do not have an underlying device in the Linux
device hierarchy. Do a regular unregister call instead of hot
unplugging such a non-existing device. Fixes a NULL dereference.
An example error message on ppc64le is shown below.
BUG: Kernel NULL pointer dereference on read at 0x00000060
Faulting instruction address: 0xc00000000080dfa4
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[...]
CPU: 2 PID: 139 Comm: systemd-udevd Not tainted 5.17.0-ae085d7f9365 #1
NIP: c00000000080dfa4 LR: c00000000080df9c CTR: c000000000797430
REGS: c000000004132fe0 TRAP: 0300 Not tainted (5.17.0-ae085d7f9365)
MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 28228282 XER: 20000000
CFAR: c00000000000c80c DAR: 0000000000000060 DSISR: 40000000 IRQMASK: 0
GPR00: c00000000080df9c c000000004133280 c00000000169d200 0000000000000029
GPR04: 00000000ffffefff c000000004132f90 c000000004132f88 0000000000000000
GPR08: c0000000015658f8 c0000000015cd200 c0000000014f57d0 0000000048228283
GPR12: 0000000000000000 c00000003fffe300 0000000020000000 0000000000000000
GPR16: 0000000000000000 0000000113fc4a40 0000000000000005 0000000113fcfb80
GPR20: 000001000f7283b0 0000000000000000 c000000000e4a588 c000000000e4a5b0
GPR24: 0000000000000001 00000000000a0000 c008000000db0168 c0000000021f6ec0
GPR28: c0000000016d65a8 c000000004b36460 0000000000000000 c0000000016d64b0
NIP [c00000000080dfa4] do_remove_conflicting_framebuffers+0x184/0x1d0
[c000000004133280] [c00000000080df9c] do_remove_conflicting_framebuffers+0x17c/0x1d0 (unreliable)
[c000000004133350] [c00000000080e4d0] remove_conflicting_framebuffers+0x60/0x150
[c0000000041333a0] [c00000000080e6f4] remove_conflicting_pci_framebuffers+0x134/0x1b0
[c000000004133450] [c008000000e70438] drm_aperture_remove_conflicting_pci_framebuffers+0x90/0x100 [drm]
[c000000004133490] [c008000000da0ce4] bochs_pci_probe+0x6c/0xa64 [bochs]
[...]
[c000000004133db0] [c00000000002aaa0] system_call_exception+0x170/0x2d0
[c000000004133e10] [c00000000000c3cc] system_call_common+0xec/0x250
The bug [1] was introduced by commit 27599aacbaef ("fbdev: Hot-unplug
firmware fb devices on forced removal"). Most firmware framebuffers
have an underlying platform device, which can be hot-unplugged
before loading the native graphics driver. OF framebuffers do not
(yet) have that device. Fix the code by unregistering the framebuffer
as before without a hot unplug.
Tested with 5.17 on qemu ppc64le emulation.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Zack Rusin <zackr@vmware.com>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: stable@vger.kernel.org # v5.11+
Cc: Helge Deller <deller@gmx.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Zheyu Ma <zheyuma97@gmail.com>
Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Link: https://lore.kernel.org/all/YkHXO6LGHAN0p1pq@debian/ # [1]
---
drivers/video/fbdev/core/fbmem.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 34d6bb1bf82e..a6bb0e438216 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1579,7 +1579,14 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
* If it's not a platform device, at least print a warning. A
* fix would add code to remove the device from the system.
*/
- if (dev_is_platform(device)) {
+ if (!device) {
+ /* TODO: Represent each OF framebuffer as its own
+ * device in the device hierarchy. For now, offb
+ * doesn't have such a device, so unregister the
+ * framebuffer as before without warning.
+ */
+ do_unregister_framebuffer(registered_fb[i]);
+ } else if (dev_is_platform(device)) {
registered_fb[i]->forced_out = true;
platform_device_unregister(to_platform_device(device));
} else {
--
2.35.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] fbdev: Fix unregistering of framebuffers without device
2022-04-04 19:44 [PATCH] fbdev: Fix unregistering of framebuffers without device Thomas Zimmermann
@ 2022-04-05 9:01 ` Daniel Vetter
2022-04-05 18:24 ` Thomas Zimmermann
2022-04-05 13:05 ` Sudip Mukherjee
2022-04-05 14:08 ` [PATCH] " Javier Martinez Canillas
2 siblings, 1 reply; 5+ messages in thread
From: Daniel Vetter @ 2022-04-05 9:01 UTC (permalink / raw)
To: Thomas Zimmermann
Cc: daniel, deller, sudipm.mukherjee, sam, javierm, zackr, hdegoede,
linux-fbdev, dri-devel, stable, Daniel Vetter, Zheyu Ma,
Xiyu Yang, Zhen Lei, Matthew Wilcox, Alex Deucher, Tetsuo Handa,
Guenter Roeck
On Mon, Apr 04, 2022 at 09:44:02PM +0200, Thomas Zimmermann wrote:
> OF framebuffers do not have an underlying device in the Linux
> device hierarchy. Do a regular unregister call instead of hot
> unplugging such a non-existing device. Fixes a NULL dereference.
> An example error message on ppc64le is shown below.
>
> BUG: Kernel NULL pointer dereference on read at 0x00000060
> Faulting instruction address: 0xc00000000080dfa4
> Oops: Kernel access of bad area, sig: 11 [#1]
> LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> [...]
> CPU: 2 PID: 139 Comm: systemd-udevd Not tainted 5.17.0-ae085d7f9365 #1
> NIP: c00000000080dfa4 LR: c00000000080df9c CTR: c000000000797430
> REGS: c000000004132fe0 TRAP: 0300 Not tainted (5.17.0-ae085d7f9365)
> MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 28228282 XER: 20000000
> CFAR: c00000000000c80c DAR: 0000000000000060 DSISR: 40000000 IRQMASK: 0
> GPR00: c00000000080df9c c000000004133280 c00000000169d200 0000000000000029
> GPR04: 00000000ffffefff c000000004132f90 c000000004132f88 0000000000000000
> GPR08: c0000000015658f8 c0000000015cd200 c0000000014f57d0 0000000048228283
> GPR12: 0000000000000000 c00000003fffe300 0000000020000000 0000000000000000
> GPR16: 0000000000000000 0000000113fc4a40 0000000000000005 0000000113fcfb80
> GPR20: 000001000f7283b0 0000000000000000 c000000000e4a588 c000000000e4a5b0
> GPR24: 0000000000000001 00000000000a0000 c008000000db0168 c0000000021f6ec0
> GPR28: c0000000016d65a8 c000000004b36460 0000000000000000 c0000000016d64b0
> NIP [c00000000080dfa4] do_remove_conflicting_framebuffers+0x184/0x1d0
> [c000000004133280] [c00000000080df9c] do_remove_conflicting_framebuffers+0x17c/0x1d0 (unreliable)
> [c000000004133350] [c00000000080e4d0] remove_conflicting_framebuffers+0x60/0x150
> [c0000000041333a0] [c00000000080e6f4] remove_conflicting_pci_framebuffers+0x134/0x1b0
> [c000000004133450] [c008000000e70438] drm_aperture_remove_conflicting_pci_framebuffers+0x90/0x100 [drm]
> [c000000004133490] [c008000000da0ce4] bochs_pci_probe+0x6c/0xa64 [bochs]
> [...]
> [c000000004133db0] [c00000000002aaa0] system_call_exception+0x170/0x2d0
> [c000000004133e10] [c00000000000c3cc] system_call_common+0xec/0x250
>
> The bug [1] was introduced by commit 27599aacbaef ("fbdev: Hot-unplug
> firmware fb devices on forced removal"). Most firmware framebuffers
> have an underlying platform device, which can be hot-unplugged
> before loading the native graphics driver. OF framebuffers do not
> (yet) have that device. Fix the code by unregistering the framebuffer
> as before without a hot unplug.
>
> Tested with 5.17 on qemu ppc64le emulation.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
> Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
> Cc: Zack Rusin <zackr@vmware.com>
> Cc: Javier Martinez Canillas <javierm@redhat.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: stable@vger.kernel.org # v5.11+
> Cc: Helge Deller <deller@gmx.de>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Zheyu Ma <zheyuma97@gmail.com>
> Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Cc: Zhen Lei <thunder.leizhen@huawei.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Cc: linux-fbdev@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Link: https://lore.kernel.org/all/YkHXO6LGHAN0p1pq@debian/ # [1]
> ---
> drivers/video/fbdev/core/fbmem.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 34d6bb1bf82e..a6bb0e438216 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1579,7 +1579,14 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
> * If it's not a platform device, at least print a warning. A
> * fix would add code to remove the device from the system.
> */
> - if (dev_is_platform(device)) {
> + if (!device) {
> + /* TODO: Represent each OF framebuffer as its own
> + * device in the device hierarchy. For now, offb
> + * doesn't have such a device, so unregister the
> + * framebuffer as before without warning.
> + */
> + do_unregister_framebuffer(registered_fb[i]);
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Might be good to have a fb_info flag for offb and then check in
register_framebuffer that everyone else does have a device? Just to make
sure we don't have more surprises here ...
-Daniel
> + } else if (dev_is_platform(device)) {
> registered_fb[i]->forced_out = true;
> platform_device_unregister(to_platform_device(device));
> } else {
> --
> 2.35.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] fbdev: Fix unregistering of framebuffers without device
2022-04-05 9:01 ` Daniel Vetter
@ 2022-04-05 18:24 ` Thomas Zimmermann
0 siblings, 0 replies; 5+ messages in thread
From: Thomas Zimmermann @ 2022-04-05 18:24 UTC (permalink / raw)
To: Daniel Vetter
Cc: deller, sudipm.mukherjee, sam, javierm, zackr, hdegoede,
linux-fbdev, dri-devel, stable, Daniel Vetter, Zheyu Ma,
Xiyu Yang, Zhen Lei, Matthew Wilcox, Alex Deucher, Tetsuo Handa,
Guenter Roeck
[-- Attachment #1.1: Type: text/plain, Size: 5792 bytes --]
Hi
Am 05.04.22 um 11:01 schrieb Daniel Vetter:
> On Mon, Apr 04, 2022 at 09:44:02PM +0200, Thomas Zimmermann wrote:
>> OF framebuffers do not have an underlying device in the Linux
>> device hierarchy. Do a regular unregister call instead of hot
>> unplugging such a non-existing device. Fixes a NULL dereference.
>> An example error message on ppc64le is shown below.
>>
>> BUG: Kernel NULL pointer dereference on read at 0x00000060
>> Faulting instruction address: 0xc00000000080dfa4
>> Oops: Kernel access of bad area, sig: 11 [#1]
>> LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
>> [...]
>> CPU: 2 PID: 139 Comm: systemd-udevd Not tainted 5.17.0-ae085d7f9365 #1
>> NIP: c00000000080dfa4 LR: c00000000080df9c CTR: c000000000797430
>> REGS: c000000004132fe0 TRAP: 0300 Not tainted (5.17.0-ae085d7f9365)
>> MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 28228282 XER: 20000000
>> CFAR: c00000000000c80c DAR: 0000000000000060 DSISR: 40000000 IRQMASK: 0
>> GPR00: c00000000080df9c c000000004133280 c00000000169d200 0000000000000029
>> GPR04: 00000000ffffefff c000000004132f90 c000000004132f88 0000000000000000
>> GPR08: c0000000015658f8 c0000000015cd200 c0000000014f57d0 0000000048228283
>> GPR12: 0000000000000000 c00000003fffe300 0000000020000000 0000000000000000
>> GPR16: 0000000000000000 0000000113fc4a40 0000000000000005 0000000113fcfb80
>> GPR20: 000001000f7283b0 0000000000000000 c000000000e4a588 c000000000e4a5b0
>> GPR24: 0000000000000001 00000000000a0000 c008000000db0168 c0000000021f6ec0
>> GPR28: c0000000016d65a8 c000000004b36460 0000000000000000 c0000000016d64b0
>> NIP [c00000000080dfa4] do_remove_conflicting_framebuffers+0x184/0x1d0
>> [c000000004133280] [c00000000080df9c] do_remove_conflicting_framebuffers+0x17c/0x1d0 (unreliable)
>> [c000000004133350] [c00000000080e4d0] remove_conflicting_framebuffers+0x60/0x150
>> [c0000000041333a0] [c00000000080e6f4] remove_conflicting_pci_framebuffers+0x134/0x1b0
>> [c000000004133450] [c008000000e70438] drm_aperture_remove_conflicting_pci_framebuffers+0x90/0x100 [drm]
>> [c000000004133490] [c008000000da0ce4] bochs_pci_probe+0x6c/0xa64 [bochs]
>> [...]
>> [c000000004133db0] [c00000000002aaa0] system_call_exception+0x170/0x2d0
>> [c000000004133e10] [c00000000000c3cc] system_call_common+0xec/0x250
>>
>> The bug [1] was introduced by commit 27599aacbaef ("fbdev: Hot-unplug
>> firmware fb devices on forced removal"). Most firmware framebuffers
>> have an underlying platform device, which can be hot-unplugged
>> before loading the native graphics driver. OF framebuffers do not
>> (yet) have that device. Fix the code by unregistering the framebuffer
>> as before without a hot unplug.
>>
>> Tested with 5.17 on qemu ppc64le emulation.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
>> Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
>> Cc: Zack Rusin <zackr@vmware.com>
>> Cc: Javier Martinez Canillas <javierm@redhat.com>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>> Cc: stable@vger.kernel.org # v5.11+
>> Cc: Helge Deller <deller@gmx.de>
>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Cc: Sam Ravnborg <sam@ravnborg.org>
>> Cc: Zheyu Ma <zheyuma97@gmail.com>
>> Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
>> Cc: Zhen Lei <thunder.leizhen@huawei.com>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Alex Deucher <alexander.deucher@amd.com>
>> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
>> Cc: Guenter Roeck <linux@roeck-us.net>
>> Cc: linux-fbdev@vger.kernel.org
>> Cc: dri-devel@lists.freedesktop.org
>> Link: https://lore.kernel.org/all/YkHXO6LGHAN0p1pq@debian/ # [1]
>> ---
>> drivers/video/fbdev/core/fbmem.c | 9 ++++++++-
>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
>> index 34d6bb1bf82e..a6bb0e438216 100644
>> --- a/drivers/video/fbdev/core/fbmem.c
>> +++ b/drivers/video/fbdev/core/fbmem.c
>> @@ -1579,7 +1579,14 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
>> * If it's not a platform device, at least print a warning. A
>> * fix would add code to remove the device from the system.
>> */
>> - if (dev_is_platform(device)) {
>> + if (!device) {
>> + /* TODO: Represent each OF framebuffer as its own
>> + * device in the device hierarchy. For now, offb
>> + * doesn't have such a device, so unregister the
>> + * framebuffer as before without warning.
>> + */
>> + do_unregister_framebuffer(registered_fb[i]);
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> Might be good to have a fb_info flag for offb and then check in
> register_framebuffer that everyone else does have a device? Just to make
> sure we don't have more surprises here ...
That exists already: all generic/firmware drivers are flagged with
FBINFO_MISC_FIRMWARE specifically for the purpose of unloading.
HW-native fbdev drivers don't have the flags and will never be unloaded.
I double-checked and of the generic drivers, (efifb, vesafb, offb,
simplefb, vga16) only offb had no device set.
Best regards
Thomas
> -Daniel
>
>
>> + } else if (dev_is_platform(device)) {
>> registered_fb[i]->forced_out = true;
>> platform_device_unregister(to_platform_device(device));
>> } else {
>> --
>> 2.35.1
>>
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
[-- Attachment #2: OpenPGP digital signature --]
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: fbdev: Fix unregistering of framebuffers without device
2022-04-04 19:44 [PATCH] fbdev: Fix unregistering of framebuffers without device Thomas Zimmermann
2022-04-05 9:01 ` Daniel Vetter
@ 2022-04-05 13:05 ` Sudip Mukherjee
2022-04-05 14:08 ` [PATCH] " Javier Martinez Canillas
2 siblings, 0 replies; 5+ messages in thread
From: Sudip Mukherjee @ 2022-04-05 13:05 UTC (permalink / raw)
To: Thomas Zimmermann
Cc: daniel, deller, sam, javierm, zackr, hdegoede, linux-fbdev,
Matthew Wilcox, Xiyu Yang, Tetsuo Handa, Daniel Vetter, Zheyu Ma,
stable, dri-devel, Zhen Lei, Alex Deucher, Guenter Roeck
On Mon, Apr 04, 2022 at 09:44:02PM +0200, Thomas Zimmermann wrote:
> OF framebuffers do not have an underlying device in the Linux
> device hierarchy. Do a regular unregister call instead of hot
> unplugging such a non-existing device. Fixes a NULL dereference.
> An example error message on ppc64le is shown below.
>
<snip>
>
> Tested with 5.17 on qemu ppc64le emulation.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
> Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
> Cc: Zack Rusin <zackr@vmware.com>
> Cc: Javier Martinez Canillas <javierm@redhat.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: stable@vger.kernel.org # v5.11+
> Cc: Helge Deller <deller@gmx.de>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Zheyu Ma <zheyuma97@gmail.com>
> Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Cc: Zhen Lei <thunder.leizhen@huawei.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Cc: linux-fbdev@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Link: https://lore.kernel.org/all/YkHXO6LGHAN0p1pq@debian/ # [1]
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
Tested-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
--
Regards
Sudip
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] fbdev: Fix unregistering of framebuffers without device
2022-04-04 19:44 [PATCH] fbdev: Fix unregistering of framebuffers without device Thomas Zimmermann
2022-04-05 9:01 ` Daniel Vetter
2022-04-05 13:05 ` Sudip Mukherjee
@ 2022-04-05 14:08 ` Javier Martinez Canillas
2 siblings, 0 replies; 5+ messages in thread
From: Javier Martinez Canillas @ 2022-04-05 14:08 UTC (permalink / raw)
To: Thomas Zimmermann, daniel, deller, sudipm.mukherjee, sam, zackr,
hdegoede
Cc: linux-fbdev, dri-devel, stable, Daniel Vetter, Zheyu Ma,
Xiyu Yang, Zhen Lei, Matthew Wilcox, Alex Deucher, Tetsuo Handa,
Guenter Roeck
Hello Thomas,
On 4/4/22 21:44, Thomas Zimmermann wrote:
> OF framebuffers do not have an underlying device in the Linux
> device hierarchy. Do a regular unregister call instead of hot
> unplugging such a non-existing device. Fixes a NULL dereference.
> An example error message on ppc64le is shown below.
>
> BUG: Kernel NULL pointer dereference on read at 0x00000060
> Faulting instruction address: 0xc00000000080dfa4
> Oops: Kernel access of bad area, sig: 11 [#1]
> LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> [...]
> CPU: 2 PID: 139 Comm: systemd-udevd Not tainted 5.17.0-ae085d7f9365 #1
> NIP: c00000000080dfa4 LR: c00000000080df9c CTR: c000000000797430
> REGS: c000000004132fe0 TRAP: 0300 Not tainted (5.17.0-ae085d7f9365)
> MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 28228282 XER: 20000000
> CFAR: c00000000000c80c DAR: 0000000000000060 DSISR: 40000000 IRQMASK: 0
> GPR00: c00000000080df9c c000000004133280 c00000000169d200 0000000000000029
> GPR04: 00000000ffffefff c000000004132f90 c000000004132f88 0000000000000000
> GPR08: c0000000015658f8 c0000000015cd200 c0000000014f57d0 0000000048228283
> GPR12: 0000000000000000 c00000003fffe300 0000000020000000 0000000000000000
> GPR16: 0000000000000000 0000000113fc4a40 0000000000000005 0000000113fcfb80
> GPR20: 000001000f7283b0 0000000000000000 c000000000e4a588 c000000000e4a5b0
> GPR24: 0000000000000001 00000000000a0000 c008000000db0168 c0000000021f6ec0
> GPR28: c0000000016d65a8 c000000004b36460 0000000000000000 c0000000016d64b0
> NIP [c00000000080dfa4] do_remove_conflicting_framebuffers+0x184/0x1d0
> [c000000004133280] [c00000000080df9c] do_remove_conflicting_framebuffers+0x17c/0x1d0 (unreliable)
> [c000000004133350] [c00000000080e4d0] remove_conflicting_framebuffers+0x60/0x150
> [c0000000041333a0] [c00000000080e6f4] remove_conflicting_pci_framebuffers+0x134/0x1b0
> [c000000004133450] [c008000000e70438] drm_aperture_remove_conflicting_pci_framebuffers+0x90/0x100 [drm]
> [c000000004133490] [c008000000da0ce4] bochs_pci_probe+0x6c/0xa64 [bochs]
> [...]
> [c000000004133db0] [c00000000002aaa0] system_call_exception+0x170/0x2d0
> [c000000004133e10] [c00000000000c3cc] system_call_common+0xec/0x250
>
> The bug [1] was introduced by commit 27599aacbaef ("fbdev: Hot-unplug
> firmware fb devices on forced removal"). Most firmware framebuffers
> have an underlying platform device, which can be hot-unplugged
> before loading the native graphics driver. OF framebuffers do not
> (yet) have that device. Fix the code by unregistering the framebuffer
> as before without a hot unplug.
>
I believe the assumption that all firmware fb would have an underlying
device was a reasonable one and it's a pity that offb doesn't...
But that is how things are and your patch is the least intrusive fix.
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
--
Best regards,
Javier Martinez Canillas
Linux Engineering
Red Hat
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-04-05 21:24 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-04-04 19:44 [PATCH] fbdev: Fix unregistering of framebuffers without device Thomas Zimmermann
2022-04-05 9:01 ` Daniel Vetter
2022-04-05 18:24 ` Thomas Zimmermann
2022-04-05 13:05 ` Sudip Mukherjee
2022-04-05 14:08 ` [PATCH] " Javier Martinez Canillas
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