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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@treblig.org>
Closes: https://lore.kernel.org/lkml/Z18dbfDAiFadsSdg@gallifrey/
Fixes: 04826f5886 ("drm/bochs: Allocate DRM device in struct bochs_device")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: virtualization@lists.linux.dev
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250103095615.231162-1-tzimmermann@suse.de
Linux kernel
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