From 84499c5d220a4f8fb0a35fa4673148525c81ea83 Mon Sep 17 00:00:00 2001
From: Thomas Zimmermann <tzimmermann@suse.de>
Date: Fri, 17 Jun 2022 14:10:27 +0200
Subject: [PATCH] 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:
BUG: KASAN: use-after-free in device_del+0x79/0x5f0
Read of size 8 at addr ffff888108185050 by task systemd-udevd/311
CPU: 0 PID: 311 Comm: systemd-udevd Tainted: G E 5.19.0-rc2-1-default+ #1689
Hardware name: HP ProLiant DL120 G7, BIOS J01 04/21/2011
Call Trace:
device_del+0x79/0x5f0
platform_device_del.part.0+0x19/0xe0
platform_device_unregister+0x1c/0x30
sysfb_disable+0x2d/0x70
remove_conflicting_framebuffers+0x1c/0xf0
remove_conflicting_pci_framebuffers+0x130/0x1a0
drm_aperture_remove_conflicting_pci_framebuffers+0x86/0xb0
mgag200_pci_probe+0x2d/0x140 [mgag200]
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 873eb3b11860 ("fbdev: Disable sysfb device registration when removing conflicting FBs")
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Changcheng Deng <deng.changcheng@zte.com.cn>
Reviewed-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
drivers/gpu/drm/drm_aperture.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/drm_aperture.c b/drivers/gpu/drm/drm_aperture.c
index 74bd4a76b253c..059fd71424f6b 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);
--
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