commit
fb561bf9abde49f7e00fdbf9ed2ccf2d86cac8ee upstream.
The efifb and simplefb drivers just render to a pre-allocated frame buffer
and rely on the display hardware being initialized before the kernel boots.
But if another driver already probed correctly and registered a fbdev, the
generic drivers shouldn't be probed since an actual driver for the display
hardware is already present.
This is more likely to occur after commit
d391c5827107 ("drivers/firmware:
move x86 Generic System Framebuffers support") since the "efi-framebuffer"
and "simple-framebuffer" platform devices are registered at a later time.
Link: https://lore.kernel.org/r/20211110200253.rfudkt3edbd3nsyj@lahvuun/
Fixes: d391c5827107 ("drivers/firmware: move x86 Generic System Framebuffers support")
Reported-by: Ilya Trukhanov <lahvuun@gmail.com>
Cc: <stable@vger.kernel.org> # 5.15.x
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Ilya Trukhanov <lahvuun@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211111115757.1351045-1-javierm@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
char *option = NULL;
efi_memory_desc_t md;
+ /*
+ * Generic drivers must not be registered if a framebuffer exists.
+ * If a native driver was probed, the display hardware was already
+ * taken and attempting to use the system framebuffer is dangerous.
+ */
+ if (num_registered_fb > 0) {
+ dev_err(&dev->dev,
+ "efifb: a framebuffer is already registered\n");
+ return -EINVAL;
+ }
+
if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI || pci_dev_disabled)
return -ENODEV;
struct simplefb_par *par;
struct resource *mem;
+ /*
+ * Generic drivers must not be registered if a framebuffer exists.
+ * If a native driver was probed, the display hardware was already
+ * taken and attempting to use the system framebuffer is dangerous.
+ */
+ if (num_registered_fb > 0) {
+ dev_err(&pdev->dev,
+ "simplefb: a framebuffer is already registered\n");
+ return -EINVAL;
+ }
+
if (fb_get_options("simplefb", NULL))
return -ENODEV;