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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 08/32] CVE-2014-3615: vbe: rework sanity checks
Backport of qemu-upstream:
* c1b886c45dc70f247300f549dce9833f3fa2def5
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
hw/vga.c | 154 ++++++++++++++++++++++++++++++++++++++------------------------
1 file changed, 95 insertions(+), 59 deletions(-)
diff --git a/hw/vga.c b/hw/vga.c
index d0c12aa..e8b1ce0 100644
--- a/hw/vga.c
+++ b/hw/vga.c
@@ -521,6 +521,93 @@ static void vga_ioport_write(void *opaque, uint32_t addr,
uint32_t val)
}
#ifdef CONFIG_BOCHS_VBE
+/*
+ * Sanity check vbe register writes.
+ *
+ * As we don't have a way to signal errors to the guest in the bochs
+ * dispi interface we'll go adjust the registers to the closest valid
+ * value.
+ */
+static void vbe_fixup_regs(VGAState *s)
+{
+ uint16_t *r = s->vbe_regs;
+ uint32_t bits, linelength, maxy, offset;
+
+ if (!(r[VBE_DISPI_INDEX_ENABLE] & VBE_DISPI_ENABLED)) {
+ /* vbe is turned off -- nothing to do */
+ return;
+ }
+
+ /* check depth */
+ switch (r[VBE_DISPI_INDEX_BPP]) {
+ case 4:
+ case 8:
+ case 16:
+ case 24:
+ case 32:
+ bits = r[VBE_DISPI_INDEX_BPP];
+ break;
+ case 15:
+ bits = 16;
+ break;
+ default:
+ bits = r[VBE_DISPI_INDEX_BPP] = 8;
+ break;
+ }
+
+ /* check width */
+ r[VBE_DISPI_INDEX_XRES] &= ~7u;
+ if (r[VBE_DISPI_INDEX_XRES] == 0) {
+ r[VBE_DISPI_INDEX_XRES] = 8;
+ }
+ if (r[VBE_DISPI_INDEX_XRES] > VBE_DISPI_MAX_XRES) {
+ r[VBE_DISPI_INDEX_XRES] = VBE_DISPI_MAX_XRES;
+ }
+ r[VBE_DISPI_INDEX_VIRT_WIDTH] &= ~7u;
+ if (r[VBE_DISPI_INDEX_VIRT_WIDTH] > VBE_DISPI_MAX_XRES) {
+ r[VBE_DISPI_INDEX_VIRT_WIDTH] = VBE_DISPI_MAX_XRES;
+ }
+ if (r[VBE_DISPI_INDEX_VIRT_WIDTH] < r[VBE_DISPI_INDEX_XRES]) {
+ r[VBE_DISPI_INDEX_VIRT_WIDTH] = r[VBE_DISPI_INDEX_XRES];
+ }
+
+ /* check height */
+ linelength = r[VBE_DISPI_INDEX_VIRT_WIDTH] * bits / 8;
+ maxy = s->vram_size / linelength;
+ if (r[VBE_DISPI_INDEX_YRES] == 0) {
+ r[VBE_DISPI_INDEX_YRES] = 1;
+ }
+ if (r[VBE_DISPI_INDEX_YRES] > VBE_DISPI_MAX_YRES) {
+ r[VBE_DISPI_INDEX_YRES] = VBE_DISPI_MAX_YRES;
+ }
+ if (r[VBE_DISPI_INDEX_YRES] > maxy) {
+ r[VBE_DISPI_INDEX_YRES] = maxy;
+ }
+
+ /* check offset */
+ if (r[VBE_DISPI_INDEX_X_OFFSET] > VBE_DISPI_MAX_XRES) {
+ r[VBE_DISPI_INDEX_X_OFFSET] = VBE_DISPI_MAX_XRES;
+ }
+ if (r[VBE_DISPI_INDEX_Y_OFFSET] > VBE_DISPI_MAX_YRES) {
+ r[VBE_DISPI_INDEX_Y_OFFSET] = VBE_DISPI_MAX_YRES;
+ }
+ offset = r[VBE_DISPI_INDEX_X_OFFSET] * bits / 8;
+ offset += r[VBE_DISPI_INDEX_Y_OFFSET] * linelength;
+ if (offset + r[VBE_DISPI_INDEX_YRES] * linelength > s->vram_size) {
+ r[VBE_DISPI_INDEX_Y_OFFSET] = 0;
+ offset = r[VBE_DISPI_INDEX_X_OFFSET] * bits / 8;
+ if (offset + r[VBE_DISPI_INDEX_YRES] * linelength > s->vram_size) {
+ r[VBE_DISPI_INDEX_X_OFFSET] = 0;
+ offset = 0;
+ }
+ }
+
+ /* update vga state */
+ r[VBE_DISPI_INDEX_VIRT_HEIGHT] = maxy;
+ s->vbe_line_offset = linelength;
+ s->vbe_start_addr = offset / 4;
+}
+
static uint32_t vbe_ioport_read_index(void *opaque, uint32_t addr)
{
VGAState *s = opaque;
@@ -588,22 +675,13 @@ static void vbe_ioport_write_data(void *opaque, uint32_t
addr, uint32_t val)
}
break;
case VBE_DISPI_INDEX_XRES:
- if ((val <= VBE_DISPI_MAX_XRES) && ((val & 7) == 0)) {
- s->vbe_regs[s->vbe_index] = val;
- }
- break;
case VBE_DISPI_INDEX_YRES:
- if (val <= VBE_DISPI_MAX_YRES) {
- s->vbe_regs[s->vbe_index] = val;
- }
- break;
case VBE_DISPI_INDEX_BPP:
- if (val == 0)
- val = 8;
- if (val == 4 || val == 8 || val == 15 ||
- val == 16 || val == 24 || val == 32) {
- s->vbe_regs[s->vbe_index] = val;
- }
+ case VBE_DISPI_INDEX_VIRT_WIDTH:
+ case VBE_DISPI_INDEX_X_OFFSET:
+ case VBE_DISPI_INDEX_Y_OFFSET:
+ s->vbe_regs[s->vbe_index] = val;
+ vbe_fixup_regs(s);
break;
case VBE_DISPI_INDEX_BANK:
if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4) {
@@ -623,19 +701,11 @@ static void vbe_ioport_write_data(void *opaque, uint32_t
addr, uint32_t val)
set_vram_mapping(s, s->lfb_addr, s->lfb_end);
}
- s->vbe_regs[VBE_DISPI_INDEX_VIRT_WIDTH] =
- s->vbe_regs[VBE_DISPI_INDEX_XRES];
- s->vbe_regs[VBE_DISPI_INDEX_VIRT_HEIGHT] =
- s->vbe_regs[VBE_DISPI_INDEX_YRES];
+ s->vbe_regs[VBE_DISPI_INDEX_VIRT_WIDTH] = 0;
s->vbe_regs[VBE_DISPI_INDEX_X_OFFSET] = 0;
s->vbe_regs[VBE_DISPI_INDEX_Y_OFFSET] = 0;
-
- if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4)
- s->vbe_line_offset = s->vbe_regs[VBE_DISPI_INDEX_XRES] >>
1;
- else
- s->vbe_line_offset = s->vbe_regs[VBE_DISPI_INDEX_XRES] *
- ((s->vbe_regs[VBE_DISPI_INDEX_BPP] + 7) >> 3);
- s->vbe_start_addr = 0;
+ s->vbe_regs[VBE_DISPI_INDEX_ENABLE] |= VBE_DISPI_ENABLED;
+ vbe_fixup_regs(s);
/* clear the screen (should be done in BIOS) */
if (!(val & VBE_DISPI_NOCLEARMEM)) {
@@ -677,40 +747,6 @@ static void vbe_ioport_write_data(void *opaque, uint32_t
addr, uint32_t val)
s->dac_8bit = (val & VBE_DISPI_8BIT_DAC) > 0;
s->vbe_regs[s->vbe_index] = val;
break;
- case VBE_DISPI_INDEX_VIRT_WIDTH:
- {
- int w, h, line_offset;
-
- if (val < s->vbe_regs[VBE_DISPI_INDEX_XRES])
- return;
- w = val;
- if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4)
- line_offset = w >> 1;
- else
- line_offset = w * ((s->vbe_regs[VBE_DISPI_INDEX_BPP] + 7)
>> 3);
- h = s->vram_size / line_offset;
- /* XXX: support weird bochs semantics ? */
- if (h < s->vbe_regs[VBE_DISPI_INDEX_YRES])
- return;
- s->vbe_regs[VBE_DISPI_INDEX_VIRT_WIDTH] = w;
- s->vbe_regs[VBE_DISPI_INDEX_VIRT_HEIGHT] = h;
- s->vbe_line_offset = line_offset;
- }
- break;
- case VBE_DISPI_INDEX_X_OFFSET:
- case VBE_DISPI_INDEX_Y_OFFSET:
- {
- int x;
- s->vbe_regs[s->vbe_index] = val;
- s->vbe_start_addr = s->vbe_line_offset *
s->vbe_regs[VBE_DISPI_INDEX_Y_OFFSET];
- x = s->vbe_regs[VBE_DISPI_INDEX_X_OFFSET];
- if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4)
- s->vbe_start_addr += x >> 1;
- else
- s->vbe_start_addr += x *
((s->vbe_regs[VBE_DISPI_INDEX_BPP] + 7) >> 3);
- s->vbe_start_addr >>= 2;
- }
- break;
default:
break;
}
--
1.7.10.4
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