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vbe: Add VBE 2.0+ OemData field to struct vbe_info 

Per the VBE 2.0 specification, the VBE controller information is 512
bytes long when the "VBE2" signature is provided, instead of the
original 256 bytes.

src/bootsplash.c uses the original pre-VBE-2.0 256-byte structure while
also filling in the "VBE2" signature, so a video BIOS that makes use of
the VBE2 OemData area could write past the end of the allocated region.

The original bootsplash code did not have this bug; it was introduced
when the bootsplash VBE structures were merged with the VGA ROM struct
definitions.

Fixes: 69e941c159 ("Merge bootsplash and VGA ROM vbe structure definitions")
Signed-off-by: Daniel Verkamp <daniel@drv.nu>
This commit is contained in:
Daniel Verkamp 2024-03-07 01:08:27 -08:00 committed by Kevin O'Connor
parent 163fd9f087
commit 5d87ff2542
2 changed files with 5 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/std/vbe.h
View File

@ -18,6 +18,8 @@ struct vbe_info {
struct segoff_s oem_product_string;
struct segoff_s oem_revision_string;
u8 reserved[222];
/* VBE 2.0 */
u8 oem_data[256];
} PACKED;
struct vbe_mode_info {

4
vgasrc/vbe.c
View File

@ -32,16 +32,18 @@ vbe_104f00(struct bregs *regs)
{
u16 seg = regs->es;
struct vbe_info *info = (void*)(regs->di+0);
size_t info_size = offsetof(struct vbe_info, oem_data);
if (GET_FARVAR(seg, info->signature) == VBE2_SIGNATURE) {
dprintf(4, "Get VBE Controller: VBE2 Signature found\n");
info_size = sizeof(*info);
} else if (GET_FARVAR(seg, info->signature) == VESA_SIGNATURE) {
dprintf(4, "Get VBE Controller: VESA Signature found\n");
} else {
dprintf(4, "Get VBE Controller: Invalid Signature\n");
}
memset_far(seg, info, 0, sizeof(*info));
memset_far(seg, info, 0, info_size);
SET_FARVAR(seg, info->signature, VESA_SIGNATURE);