linux-kernel - [PATCH 2/2] video: vga16fb: Only probe for EGA and VGA 16 color graphic cards

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Date:   Fri,  7 Jan 2022 12:07:23 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Kris Karas <bugs-a21@...nlit-rail.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        stable@...r.kernel.org, Borislav Petkov <bp@...e.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org
Subject: [PATCH 2/2] video: vga16fb: Only probe for EGA and VGA 16 color graphic cards

The vga16fb framebuffer driver only supports Enhanced Graphics Adapter
(EGA) and Video Graphics Array (VGA) 16 color graphic cards.

But it doesn't check if the adapter is one of those or if a VGA16 mode
is used. This means that the driver will be probed even if a VESA BIOS
Extensions (VBE) or Graphics Output Protocol (GOP) interface is used.

This issue has been present for a long time but it was only exposed by
commit d391c5827107 ("drivers/firmware: move x86 Generic System
Framebuffers support") since the platform device registration to match
the {vesa,efi}fb drivers is done later as a consequence of that change.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=215001
Fixes: d391c5827107 ("drivers/firmware: move x86 Generic System Framebuffers support")
Reported-by: Kris Karas <bugs-a21@...nlit-rail.com>
Cc: <stable@...r.kernel.org> # 5.15.x
Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
Tested-by: Kris Karas <bugs-a21@...nlit-rail.com>
---

 drivers/video/fbdev/vga16fb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c
index 3347c9b6a332..72b6aeceeff8 100644
--- a/drivers/video/fbdev/vga16fb.c
+++ b/drivers/video/fbdev/vga16fb.c
@@ -1422,6 +1422,18 @@ static int __init vga16fb_init(void)
 
 	vga16fb_setup(option);
 #endif
+
+	/* only EGA and VGA in 16 color graphic mode are supported */
+	if (screen_info.orig_video_isVGA != VIDEO_TYPE_EGAC &&
+	    screen_info.orig_video_isVGA != VIDEO_TYPE_VGAC)
+		return -ENODEV;
+
+	if (screen_info.orig_video_mode != 0x0D &&	/* 320x200/4 (EGA) */
+	    screen_info.orig_video_mode != 0x0E &&	/* 640x200/4 (EGA) */
+	    screen_info.orig_video_mode != 0x10 &&	/* 640x350/4 (EGA) */
+	    screen_info.orig_video_mode != 0x12)	/* 640x480/4 (VGA) */
+		return -ENODEV;
+
 	ret = platform_driver_register(&vga16fb_driver);
 
 	if (!ret) {
-- 
2.33.1