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: 69e941c159ed ("Merge bootsplash and VGA ROM vbe structure definitions")
Signed-off-by: Daniel Verkamp <daniel(a)drv.nu>
---
v2 fixes the inverse bug introduced by the original patch - the vgabios
would memset too much data if the caller did not request VBE2 data.
src/std/vbe.h | 2 ++
vgasrc/vbe.c | 4 +++-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/src/std/vbe.h b/src/std/vbe.h
index 94b4ad86..fe96f5ec 100644
--- a/src/std/vbe.h
+++ b/src/std/vbe.h
@@ -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 {
diff --git a/vgasrc/vbe.c b/vgasrc/vbe.c
index 66afb011..91abc9ab 100644
--- a/vgasrc/vbe.c
+++ b/vgasrc/vbe.c
@@ -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);
--
2.43.0