From: Thomas Zimmermann <tzimmermann@xxxxxxx>
drm/aperture: Run fbdev removal before internal helpers
Always run fbdev removal first to remove simpledrm via
sysfb_disable(). This clears the internal state. The later call
to drm_aperture_detach_drivers() then does nothing. Otherwise,
with drm_aperture_detach_drivers() running first, the call to
sysfb_disable() uses inconsistent state.
Example backtrace show below:
[ 11.663422] ==================================================================
[ 11.663426] BUG: KASAN: use-after-free in device_del+0x79/0x5f0
[ 11.663435] Read of size 8 at addr ffff888108185050 by task systemd-udevd/311
[ 11.663440] CPU: 0 PID: 311 Comm: systemd-udevd Tainted: G E 5
.19.0-rc2-1-default+ #1689
[ 11.663445] Hardware name: HP ProLiant DL120 G7, BIOS J01 04/21/2011
[ 11.663447] Call Trace:
[ 11.663449] <TASK>
[ 11.663451] ? device_del+0x79/0x5f0
[ 11.663456] dump_stack_lvl+0x5b/0x73
[ 11.663462] print_address_description.constprop.0+0x1f/0x1b0
[ 11.663468] ? device_del+0x79/0x5f0
[ 11.663471] ? device_del+0x79/0x5f0
[ 11.663475] print_report.cold+0x3c/0x21c
[ 11.663481] ? lock_acquired+0x87/0x1e0
[ 11.663484] ? lock_acquired+0x87/0x1e0
[ 11.663489] ? device_del+0x79/0x5f0
[ 11.663492] kasan_report+0xbf/0xf0
[ 11.663498] ? device_del+0x79/0x5f0
[ 11.663503] device_del+0x79/0x5f0
[ 11.663509] ? device_remove_attrs+0x170/0x170
[ 11.663514] ? lock_is_held_type+0xe8/0x140
[ 11.663523] platform_device_del.part.0+0x19/0xe0
[ 11.663530] platform_device_unregister+0x1c/0x30
[ 11.663535] sysfb_disable+0x2d/0x70
[ 11.663540] remove_conflicting_framebuffers+0x1c/0xf0
[ 11.663546] remove_conflicting_pci_framebuffers+0x130/0x1a0
[ 11.663554] drm_aperture_remove_conflicting_pci_framebuffers+0x86/0xb0
[ 11.663561] ? mgag200_pci_remove+0x30/0x30 [mgag200]
[ 11.663578] mgag200_pci_probe+0x2d/0x140 [mgag200]
Reported-by: Zack Rusin <zackr@xxxxxxxxxx>
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Reviewed-by: Zack Rusin <zackr@xxxxxxxxxx>
Fixes: 873eb3b11860 ("fbdev: Disable sysfb device registration when removing conflicting FBs")
Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Helge Deller <deller@xxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
Cc: Changcheng Deng <deng.changcheng@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20220617121027.30273-1-tzimmermann@xxxxxxx
diff --git a/drivers/gpu/drm/drm_aperture.c b/drivers/gpu/drm/drm_aperture.c
index blahblah..blahblah 100644
--- a/drivers/gpu/drm/drm_aperture.c
+++ b/drivers/gpu/drm/drm_aperture.c
@@ -329,7 +329,20 @@ int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
const struct drm_driver *req_driver)
{
resource_size_t base, size;
- int bar, ret = 0;
+ int bar, ret;
+
+ /*
+ * WARNING: Apparently we must kick fbdev drivers before vgacon,
+ * otherwise the vga fbdev driver falls over.
+ */
+#if IS_REACHABLE(CONFIG_FB)
+ ret = remove_conflicting_pci_framebuffers(pdev, req_driver->name);
+ if (ret)
+ return ret;
+#endif
+ ret = vga_remove_vgacon(pdev);
+ if (ret)
+ return ret;
for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
@@ -339,15 +352,6 @@ int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
drm_aperture_detach_drivers(base, size);
}
- /*
- * WARNING: Apparently we must kick fbdev drivers before vgacon,
- * otherwise the vga fbdev driver falls over.
- */
-#if IS_REACHABLE(CONFIG_FB)
- ret = remove_conflicting_pci_framebuffers(pdev, req_driver->name);
-#endif
- if (ret == 0)
- ret = vga_remove_vgacon(pdev);
- return ret;
+ return 0;
}
EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);
--
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1904
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