[xen stable-4.16] efifb: ignore frame buffer with invalid configuration

[patchbot@xxxxxxx]

commit 4759d80fd291b144069a9705118fdee19bed9595
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Nov 28 11:45:45 2022 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Nov 28 11:45:45 2022 +0100

    efifb: ignore frame buffer with invalid configuration
    
    On one of my boxes when the HDMI cable is not plugged in the
    FrameBufferBase of the EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE structure is
    set to 0 by the firmware (while some of the other fields looking
    plausible).
    
    Such (bogus address) ends up mapped in vesa_init(), and since it
    overlaps with a RAM region the whole system goes down pretty badly,
    see:
    
    (XEN) vesafb: framebuffer at 0x0000000000000000, mapped to 
0xffff82c000201000, using 35209k, total 35209k
    (XEN) vesafb: mode is 0x37557x32, linelength=960, font 8x16
    (XEN) vesafb: Truecolor: size=8:8:8:8, shift=24:0:8:16
    (XEN) (XEN) (XEN) (XEN) (XEN) (XEN) (XEN) (XEN) �ERROR: Class:0; 
Subclass:0; Operation: 0
    ERROR: No ConOut
    ERROR: No ConIn
    
    Do like Linux and prevent using the EFI Frame Buffer if the base
    address is 0.  This is inline with the logic in Linuxes
    fb_base_is_valid() function at drivers/video/fbdev/efifb.c v6.0.9.
    
    See also Linux commit 133bb070e94ab41d750c6f2160c8843e46f11b78 for
    further reference.
    
    Also prevent using Frame Buffers that have a 0 height or width, as
    those are also invalid.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 57f07cca82521088cca0c1fc36d6ffd06cb7de80
    master date: 2022-11-21 12:21:51 +0100
---
 xen/arch/x86/efi/efi-boot.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index d996016223..01e63c0dd4 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -506,6 +506,13 @@ static void __init 
efi_arch_video_init(EFI_GRAPHICS_OUTPUT_PROTOCOL *gop,
 #ifdef CONFIG_VIDEO
     int bpp = 0;
 
+    if ( !gop->Mode->FrameBufferBase || !mode_info->HorizontalResolution ||
+         !mode_info->VerticalResolution )
+    {
+        PrintErr(L"Invalid Frame Buffer configuration found\r\n");
+        return;
+    }
+
     switch ( mode_info->PixelFormat )
     {
     case PixelRedGreenBlueReserved8BitPerColor:
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16