| From 0f525289ff0ddeb380813bd81e0f9bdaaa1c9078 Mon Sep 17 00:00:00 2001 |
| From: Thomas Zimmermann <tzimmermann@suse.de> |
| Date: Mon, 4 Apr 2022 21:44:02 +0200 |
| Subject: fbdev: Fix unregistering of framebuffers without device |
| |
| From: Thomas Zimmermann <tzimmermann@suse.de> |
| |
| commit 0f525289ff0ddeb380813bd81e0f9bdaaa1c9078 upstream. |
| |
| 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> |
| Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
| Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> |
| Tested-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk> |
| 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] |
| Link: https://patchwork.freedesktop.org/patch/msgid/20220404194402.29974-1-tzimmermann@suse.de |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/video/fbdev/core/fbmem.c | 9 ++++++++- |
| 1 file changed, 8 insertions(+), 1 deletion(-) |
| |
| --- a/drivers/video/fbdev/core/fbmem.c |
| +++ b/drivers/video/fbdev/core/fbmem.c |
| @@ -1581,7 +1581,14 @@ static void do_remove_conflicting_frameb |
| * 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 { |