Am 21.08.24 um 21:11 schrieb Alex Deucher:

In aperture_remove_conflicting_pci_devices(), we currently only call sysfb_disable() on vga class devices. This leads to the following problem when the pimary device is not VGA compatible:

1. A PCI device with a non-VGA class is the boot display
2. That device is probed first and it is not a VGA device so sysfb_disable() is not called, but the device resources are freed by aperture_detach_platform_device()
3. Non-primary GPU has a VGA class and it ends up calling sysfb_disable()
4. NULL pointer dereference via sysfb_disable() since the resources have already been freed by aperture_detach_platform_device() when it was called by the other device.

Fix this by passing a device pointer to sysfb_disable() and checking the device to determine if we should execute it or not.

v2: Fix build when CONFIG_SCREEN_INFO is not set v3: Move device check into the mutex Drop primary variable in aperture_remove_conflicting_pci_devices() Drop __init on pci sysfb_pci_dev_is_enabled()

Fixes: 5ae3716cfdcd ("video/aperture: Only remove sysfb on the default vga pci device") Cc: Javier Martinez Canillas javierm@redhat.com Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Helge Deller deller@gmx.de Cc: Sam Ravnborg sam@ravnborg.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Alex Deucher alexander.deucher@amd.com Cc: stable@vger.kernel.org

This change also makes aperture_remove_conflicting_pci_devices() much cleaner. Thanks a lot. Reviewed-by: Thomas Zimmermann tzimmermann@suse.de

---

drivers/firmware/sysfb.c | 19 +++++++++++++------ drivers/of/platform.c | 2 +- drivers/video/aperture.c | 11 +++-------- include/linux/sysfb.h | 4 ++-- 4 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/drivers/firmware/sysfb.c b/drivers/firmware/sysfb.c index 880ffcb50088..ac4680dc463f 100644 --- a/drivers/firmware/sysfb.c +++ b/drivers/firmware/sysfb.c @@ -39,6 +39,8 @@ static struct platform_device *pd; static DEFINE_MUTEX(disable_lock); static bool disabled; +static struct device *sysfb_parent_dev(const struct screen_info *si);

• static bool sysfb_unregister(void) { if (IS_ERR_OR_NULL(pd))

@@ -52,6 +54,7 @@ static bool sysfb_unregister(void) /**

• sysfb_disable() - disable the Generic System Framebuffers support

• • @dev: the device to check if non-NULL
  • This disables the registration of system framebuffer devices that match the
  • generic drivers that make use of the system framebuffer set up by firmware.

@@ -61,17 +64,21 @@ static bool sysfb_unregister(void)

• Context: The function can sleep. A @disable_lock mutex is acquired to serialize

•      against sysfb_init(), that registers a system framebuffer device.
  

*/ -void sysfb_disable(void) +void sysfb_disable(struct device *dev) {

• struct screen_info *si = &screen_info;
• mutex_lock(&disable_lock);

• sysfb_unregister();
• disabled = true;

• if (!dev || dev == sysfb_parent_dev(si)) {

• sysfb_unregister();
  

• disabled = true;
  

• } mutex_unlock(&disable_lock); } EXPORT_SYMBOL_GPL(sysfb_disable);

#if defined(CONFIG_PCI) -static __init bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev) +static bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev) { /* * TODO: Try to integrate this code into the PCI subsystem @@ -87,13 +94,13 @@ static __init bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev) return true; } #else -static __init bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev) +static bool sysfb_pci_dev_is_enabled(struct pci_dev *pdev) { return false; } #endif -static __init struct device *sysfb_parent_dev(const struct screen_info *si) +static struct device *sysfb_parent_dev(const struct screen_info *si) { struct pci_dev *pdev; diff --git a/drivers/of/platform.c b/drivers/of/platform.c index 389d4ea6bfc1..ef622d41eb5b 100644 --- a/drivers/of/platform.c +++ b/drivers/of/platform.c @@ -592,7 +592,7 @@ static int __init of_platform_default_populate_init(void) * This can happen for example on DT systems that do EFI * booting and may provide a GOP handle to the EFI stub. */

• 	sysfb_disable();
  

• 	sysfb_disable(NULL);
  of_platform_device_create(node, NULL, NULL);
  of_node_put(node);
  

  }

diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c index 561be8feca96..2b5a1e666e9b 100644 --- a/drivers/video/aperture.c +++ b/drivers/video/aperture.c @@ -293,7 +293,7 @@ int aperture_remove_conflicting_devices(resource_size_t base, resource_size_t si * ask for this, so let's assume that a real driver for the display * was already probed and prevent sysfb to register devices later. */

• sysfb_disable();

• sysfb_disable(NULL);

aperture_detach_devices(base, size); @@ -346,15 +346,10 @@ EXPORT_SYMBOL(__aperture_remove_legacy_vga_devices); */ int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *name) {

• bool primary = false; resource_size_t base, size; int bar, ret = 0;

• if (pdev == vga_default_device())

• primary = true;
  

• if (primary)

• sysfb_disable();
  

• sysfb_disable(&pdev->dev);

for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) { if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) @@ -370,7 +365,7 @@ int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *na * that consumes the VGA framebuffer I/O range. Remove this * device as well. */

• if (primary)

• if (pdev == vga_default_device()) ret = __aperture_remove_legacy_vga_devices(pdev);

return ret; diff --git a/include/linux/sysfb.h b/include/linux/sysfb.h index c9cb657dad08..bef5f06a91de 100644 --- a/include/linux/sysfb.h +++ b/include/linux/sysfb.h @@ -58,11 +58,11 @@ struct efifb_dmi_info { #ifdef CONFIG_SYSFB -void sysfb_disable(void); +void sysfb_disable(struct device *dev); #else /* CONFIG_SYSFB */ -static inline void sysfb_disable(void) +static inline void sysfb_disable(struct device *dev) { }