From: Javier Martinez Canillas javierm@redhat.com
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-javie... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/video/fbdev/efifb.c | 11 +++++++++++ drivers/video/fbdev/simplefb.c | 11 +++++++++++ 2 files changed, 22 insertions(+)
--- a/drivers/video/fbdev/efifb.c +++ b/drivers/video/fbdev/efifb.c @@ -351,6 +351,17 @@ static int efifb_probe(struct platform_d 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;
--- a/drivers/video/fbdev/simplefb.c +++ b/drivers/video/fbdev/simplefb.c @@ -407,6 +407,17 @@ static int simplefb_probe(struct platfor 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;