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Message-ID: <Z2AvS_8xgBhnF4CW@gallifrey>
Date: Mon, 16 Dec 2024 13:46:51 +0000
From: "Dr. David Alan Gilbert" <linux@...blig.org>
To: Thomas Zimmermann <tzimmermann@...e.de>
Cc: kraxel@...hat.com, virtualization@...ts.linux.dev,
linux-kernel@...r.kernel.org,
dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: a bochs-drm (?) oops on head
* Thomas Zimmermann (tzimmermann@...e.de) wrote:
> Hi
Hi Thomas,
Thanks for the reply.
> Am 15.12.24 um 19:18 schrieb Dr. David Alan Gilbert:
> > Hey Gerd, Thomas,
> > I've got the following oops that looks bochs-drm related on the current
> > HEAD ( 4800575d8c0b2f354ab05ab1c4749e45e213bf73 ) and it's been there
> > for at least a few days; this is
> [...]
> >
> > The oops has :
> > [ 78.463760][ T1] bochs_pci_driver_init+0x8a/0xc0
> >
> > in it, hence why I'm blaming that.
> > (Other odd observation, the Tuxen flicker heavily during booting!)
> >
> > [ 72.756014][ T1] bochs-drm 0000:00:02.0: vgaarb: deactivate vga console
> > [ 72.758258][ T1] [drm] Found bochs VGA, ID 0xb0c5.
> > [ 72.758793][ T1] [drm] Framebuffer size 16384 kB @ 0xfd000000, mmio @ 0xfebf0000.
> > [ 72.767777][ T1] [drm] Initialized bochs-drm 1.0.0 for 0000:00:02.0 on minor 2
> > [ 72.839222][ T1] fbcon: bochs-drmdrmfb (fb1) is primary device
> > [ 72.839311][ T1] fbcon: Remapping primary device, fb1, to tty 1-63
> > [ 78.402163][ T1] bochs-drm 0000:00:02.0: [drm] fb1: bochs-drmdrmfb frame buffer device
> > [ 78.459984][ T1] BUG: unable to handle page fault for address: ffff8dd345604004
> > [ 78.463246][ T1] #PF: supervisor write access in kernel mode
> > [ 78.463760][ T1] #PF: error_code(0x0002) - not-present page
> > [ 78.463760][ T1] PGD 72001067 P4D 72001067 PUD 72002067 PMD 7fbe1067 PTE 800ffffffa9fb060
> > [ 78.463760][ T1] Oops: Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI
> > [ 78.463760][ T1] CPU: 2 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W N 6.13.0-rc2+ #363 6c653a430ed30aae3dac648429c492a2726da3d7
> > [ 78.463760][ T1] Tainted: [W]=WARN, [N]=TEST
> > [ 78.463760][ T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
> > [ 78.463760][ T1] RIP: 0010:devm_drm_dev_init_release+0x4e/0x140
> [...]
> >
> > [ 78.463760][ T1] ---[ end Kernel panic - not syncing: Fatal exception ]---
> >
> >
> > The config is a fairly full yes-config ish; see attached.
>
> Thanks for reporting. I've been able to reproduce the problem by setting
> CONFIG_DEBUG_TEST_DRIVER_REMOVE <https://elixir.bootlin.com/linux/v6.13-rc2/K/ident/CONFIG_DEBUG_TEST_DRIVER_REMOVE>=y.
Ah OK, so fairly obscure (I'm running something close to a all-yes-config
because I'm mostly build testing obscure stuff).
> The attached patch fixes the problem for me. Could you please test and
> report back the results.
That gets me a different oops; this was run with:
qemu-system-x86_64 -M pc -cpu host --enable-kvm -smp 4 -m 2G -kernel /discs/fast/kernel/arch/x86/boot/bzImage -append "console=tty0 console=ttyS0 root=/dev/vdb1 single" -drive if=virtio,file=/discs/more/images/debian12-64scan.qcow2
It looks to me if it made the mistake of trying to print something in the middle of being removed:
[ 73.569852][ T1] bochs-drm 0000:00:02.0: vgaarb: deactivate vga console
[ 73.571802][ T1] [drm] Found bochs VGA, ID 0xb0c5.
[ 73.572787][ T1] [drm] Framebuffer size 16384 kB @ 0xfd000000, mmio @ 0xfebf0000.
[ 73.581626][ T1] [drm] Initialized bochs-drm 1.0.0 for 0000:00:02.0 on minor 2
[ 73.650048][ T1] fbcon: bochs-drmdrmfb (fb1) is primary device
[ 73.650134][ T1] fbcon: Remapping primary device, fb1, to tty 1-63
[ 79.276550][ T1] bochs-drm 0000:00:02.0: [drm] fb1: bochs-drmdrmfb frame buffer device
[ 79.346726][ T1] bochs-drm 0000:00:02.0: vgaarb: deactivate vga console
[ 79.348731][ T1] BUG: kernel NULL pointer dereference, address: 000000000000020c
[ 79.348799][ T1] #PF: supervisor write access in kernel mode
[ 79.348857][ T1] #PF: error_code(0x0002) - not-present page
[ 79.348913][ T1] PGD 0 P4D 0
[ 79.348999][ T1] Oops: Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI
[ 79.349107][ T1] CPU: 2 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W N 6.13.0-rc2+ #373 5a5c0ce8f09b0b72067981f01985e201a0118bb6
[ 79.349268][ T1] Tainted: [W]=WARN, [N]=TEST
[ 79.349313][ T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
[ 79.349377][ T1] RIP: 0010:fbcon_cursor+0xa9/0x3c0
[ 79.349524][ T1] Code: c0 05 00 00 66 89 44 24 06 e8 f3 35 2a fd 0f b7 bb c0 05 00 00 e8 27 b8 e9 fc 49 8d bc 24 0c 02 00 00 49 89 c7 e8 d7 3d 2a fd <45> 89 bc 24 0c 02 00 00 48 8d bd e0 05 00 00 e8 c3 3b 2a fd 44 8b
[ 79.349628][ T1] RSP: 0018:ffffb927800136c0 EFLAGS: 00010046
[ 79.349716][ T1] RAX: 0000000000000000 RBX: ffff9835810a8800 RCX: 0000000000000000
[ 79.349808][ T1] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 79.349879][ T1] RBP: ffff983585d07000 R08: 0000000000000000 R09: 0000000000000000
[ 79.349952][ T1] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[ 79.350024][ T1] R13: 0000000000000000 R14: ffff983585d075e8 R15: 0000000000000032
[ 79.350101][ T1] FS: 0000000000000000(0000) GS:ffff9835fd200000(0000) knlGS:0000000000000000
[ 79.350196][ T1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 79.350278][ T1] CR2: 000000000000020c CR3: 000000004d920000 CR4: 0000000000350ef0
[ 79.350344][ T1] Call Trace:
[ 79.350373][ T1] <TASK>
[ 79.350413][ T1] ? __die+0x23/0x80
[ 79.350540][ T1] ? page_fault_oops+0x21c/0x240
[ 79.350675][ T1] ? do_user_addr_fault+0x893/0x1180
[ 79.350798][ T1] ? srso_return_thunk+0x5/0x7f
[ 79.350904][ T1] ? exc_page_fault+0x3f/0x180
[ 79.351066][ T1] ? exc_page_fault+0x87/0x180
[ 79.351211][ T1] ? asm_exc_page_fault+0x26/0x40
[ 79.351379][ T1] ? fbcon_cursor+0xa9/0x3c0
[ 79.351542][ T1] hide_cursor+0x66/0x1c0
[ 79.351656][ T1] vt_console_print+0x9b1/0xa40
[ 79.351813][ T1] ? srso_return_thunk+0x5/0x7f
[ 79.351920][ T1] ? irq_trace+0x84/0xc0
[ 79.352029][ T1] ? srso_return_thunk+0x5/0x7f
[ 79.352153][ T1] ? console_emit_next_record+0x1fe/0x440
[ 79.352254][ T1] console_emit_next_record+0x232/0x440
[ 79.352333][ T1] ? console_emit_next_record+0x1fe/0x440
[ 79.352450][ T1] console_flush_all+0x590/0x7c0
[ 79.352531][ T1] ? console_flush_all+0x26/0x7c0
[ 79.352601][ T1] console_unlock+0xf9/0x280
[ 79.352601][ T1] vprintk_emit+0x572/0x5c0
[ 79.352601][ T1] dev_vprintk_emit+0x70/0xc0
[ 79.352601][ T1] ? __mutex_lock+0x380/0xd40
[ 79.352601][ T1] dev_printk_emit+0x7f/0xc0
[ 79.352601][ T1] __dev_printk+0x89/0x100
[ 79.352601][ T1] _dev_info+0xba/0xf5
[ 79.352601][ T1] vga_remove_vgacon.cold+0x18/0xc0
[ 79.352601][ T1] aperture_remove_conflicting_pci_devices+0x142/0x1c0
[ 79.352601][ T1] ? __pfx_bochs_pci_probe+0x40/0x40
[ 79.352601][ T1] bochs_pci_probe+0x30/0x380
[ 79.352601][ T1] local_pci_probe+0x88/0x100
[ 79.352601][ T1] pci_call_probe+0x126/0x340
[ 79.352601][ T1] ? srso_return_thunk+0x5/0x7f
[ 79.352601][ T1] ? pci_match_device+0x287/0x380
[ 79.352601][ T1] pci_device_probe+0x154/0x280
[ 79.352601][ T1] ? __pfx_pci_device_probe+0x40/0x40
[ 79.352601][ T1] really_probe+0x411/0x780
[ 79.352601][ T1] __driver_probe_device+0x194/0x280
[ 79.352601][ T1] driver_probe_device+0x6f/0x1c0
[ 79.352601][ T1] __driver_attach+0x204/0x380
[ 79.352601][ T1] ? __pfx___driver_attach+0x40/0x40
[ 79.352601][ T1] bus_for_each_dev+0xe3/0x180
[ 79.352601][ T1] driver_attach+0x3a/0x80
[ 79.352601][ T1] bus_add_driver+0x1fd/0x3c0
[ 79.352601][ T1] driver_register+0x11d/0x1c0
[ 79.352601][ T1] __pci_register_driver+0x105/0x140
[ 79.352601][ T1] bochs_pci_driver_init+0x8a/0xc0
[ 79.352601][ T1] ? __pfx_bochs_pci_driver_init+0x40/0x40
[ 79.352601][ T1] do_one_initcall+0xa7/0x500
[ 79.352601][ T1] do_initcalls+0x1d5/0x240
[ 79.352601][ T1] kernel_init_freeable+0x1e4/0x280
[ 79.352601][ T1] ? __pfx_kernel_init+0x40/0x40
[ 79.352601][ T1] kernel_init+0x2a/0x280
[ 79.352601][ T1] ret_from_fork+0x4d/0x80
[ 79.352601][ T1] ? __pfx_kernel_init+0x40/0x40
[ 79.352601][ T1] ret_from_fork_asm+0x22/0x80
[ 79.352601][ T1] </TASK>
[ 79.352601][ T1] Modules linked in:
[ 79.352601][ T1] CR2: 000000000000020c
[ 79.352601][ T1] ---[ end trace 0000000000000000 ]---
[ 79.352601][ T1] RIP: 0010:fbcon_cursor+0xa9/0x3c0
[ 79.352601][ T1] Code: c0 05 00 00 66 89 44 24 06 e8 f3 35 2a fd 0f b7 bb c0 05 00 00 e8 27 b8 e9 fc 49 8d bc 24 0c 02 00 00 49 89 c7 e8 d7 3d 2a fd <45> 89 bc 24 0c 02 00 00 48 8d bd e0 05 00 00 e8 c3 3b 2a fd 44 8b
[ 79.352601][ T1] RSP: 0018:ffffb927800136c0 EFLAGS: 00010046
[ 79.352601][ T1] RAX: 0000000000000000 RBX: ffff9835810a8800 RCX: 0000000000000000
[ 79.352601][ T1] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 79.352601][ T1] RBP: ffff983585d07000 R08: 0000000000000000 R09: 0000000000000000
[ 79.352601][ T1] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[ 79.352601][ T1] R13: 0000000000000000 R14: ffff983585d075e8 R15: 0000000000000032
[ 79.352601][ T1] FS: 0000000000000000(0000) GS:ffff9835fd200000(0000) knlGS:0000000000000000
[ 79.352601][ T1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 79.352601][ T1] CR2: 000000000000020c CR3: 000000004d920000 CR4: 0000000000350ef0
[ 79.352601][ T1] Kernel panic - not syncing: Fatal exception
[ 79.352601][ T1] Kernel Offset: 0xf800000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[ 79.352601][ T1] ---[ end Kernel panic - not syncing: Fatal exception ]---
> Best regards
> Thomas
>
>
> >
> > Dave
> >
>
> --
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Frankenstrasse 146, 90461 Nuernberg, Germany
> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
> HRB 36809 (AG Nuernberg)
> From bebba3b34d5df5aa7c882f080633b43ddb87f4ad Mon Sep 17 00:00:00 2001
> From: Thomas Zimmermann <tzimmermann@...e.de>
> Date: Mon, 16 Dec 2024 09:21:46 +0100
> Subject: [PATCH] drm/bochs: Do not put DRM device in PCI remove callback
>
> Removing the bochs PCI device should mark the DRM device as unplugged
> without removing it. Hence clear the respective call to drm_dev_put()
> from bochs_pci_remove().
>
> Fixes a double unref in devm_drm_dev_init_release(). An example error
> message is shown below:
>
> [ 32.958338] BUG: KASAN: use-after-free in drm_dev_put.part.0+0x1b/0x90
> [ 32.958850] Write of size 4 at addr ffff888152134004 by task (udev-worker)/591
> [ 32.959574] CPU: 3 UID: 0 PID: 591 Comm: (udev-worker) Tainted: G E 6.13.0-rc2-1-default+ #3417
> [ 32.960316] Tainted: [E]=UNSIGNED_MODULE
> [ 32.960637] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014
> [ 32.961429] Call Trace:
> [ 32.961433] <TASK>
> [ 32.961439] dump_stack_lvl+0x68/0x90
> [ 32.961452] print_address_description.constprop.0+0x88/0x330
> [ 32.961461] ? preempt_count_sub+0x14/0xc0
> [ 32.961473] print_report+0xe2/0x1d0
> [ 32.961479] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 32.963725] ? __virt_addr_valid+0x143/0x320
> [ 32.964077] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 32.964463] ? drm_dev_put.part.0+0x1b/0x90
> [ 32.964817] kasan_report+0xce/0x1a0
> [ 32.965123] ? drm_dev_put.part.0+0x1b/0x90
> [ 32.965474] kasan_check_range+0xff/0x1c0
> [ 32.965806] drm_dev_put.part.0+0x1b/0x90
> [ 32.966138] release_nodes+0x84/0xc0
> [ 32.966447] devres_release_all+0xd2/0x110
> [ 32.966788] ? __pfx_devres_release_all+0x10/0x10
> [ 32.967177] ? preempt_count_sub+0x14/0xc0
> [ 32.967523] device_unbind_cleanup+0x16/0xc0
> [ 32.967886] really_probe+0x1b7/0x570
> [ 32.968207] __driver_probe_device+0xca/0x1b0
> [ 32.968568] driver_probe_device+0x4a/0xf0
> [ 32.968907] __driver_attach+0x10b/0x290
> [ 32.969239] ? __pfx___driver_attach+0x10/0x10
> [ 32.969598] bus_for_each_dev+0xc0/0x110
> [ 32.969923] ? __pfx_bus_for_each_dev+0x10/0x10
> [ 32.970291] ? bus_add_driver+0x17a/0x2b0
> [ 32.970622] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 32.971011] bus_add_driver+0x19a/0x2b0
> [ 32.971335] driver_register+0xd8/0x160
> [ 32.971671] ? __pfx_bochs_pci_driver_init+0x10/0x10 [bochs]
> [ 32.972130] do_one_initcall+0xba/0x390
> [...]
>
> After unplugging the DRM device, clients will close their references.
> Closing the final reference will also release the DRM device.
>
> Reported-by: Dr. David Alan Gilbert <dave@...blig.org>
> Closes: https://lore.kernel.org/lkml/Z18dbfDAiFadsSdg@gallifrey/
> Fixes: 04826f588682 ("drm/bochs: Allocate DRM device in struct bochs_device")
> Cc: Thomas Zimmermann <tzimmermann@...e.de>
> Cc: Gerd Hoffmann <kraxel@...hat.com>
> Cc: virtualization@...ts.linux.dev
> Signed-off-by: Thomas Zimmermann <tzimmermann@...e.de>
> ---
> drivers/gpu/drm/tiny/bochs.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c
> index 89a699370a59..c67e1f906785 100644
> --- a/drivers/gpu/drm/tiny/bochs.c
> +++ b/drivers/gpu/drm/tiny/bochs.c
> @@ -757,7 +757,6 @@ static void bochs_pci_remove(struct pci_dev *pdev)
>
> drm_dev_unplug(dev);
> drm_atomic_helper_shutdown(dev);
> - drm_dev_put(dev);
> }
>
> static void bochs_pci_shutdown(struct pci_dev *pdev)
> --
> 2.47.1
>
--
-----Open up your eyes, open up your mind, open up your code -------
/ Dr. David Alan Gilbert | Running GNU/Linux | Happy \
\ dave @ treblig.org | | In Hex /
\ _________________________|_____ http://www.treblig.org |_______/
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