diff options
Diffstat (limited to 'system/xen/patches/xsa179-qemuu-4.6-0005-vga-make-sure-vga-register-setup-for-vbe-stays-intac.patch')
| -rw-r--r-- | system/xen/patches/xsa179-qemuu-4.6-0005-vga-make-sure-vga-register-setup-for-vbe-stays-intac.patch | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/system/xen/patches/xsa179-qemuu-4.6-0005-vga-make-sure-vga-register-setup-for-vbe-stays-intac.patch b/system/xen/patches/xsa179-qemuu-4.6-0005-vga-make-sure-vga-register-setup-for-vbe-stays-intac.patch new file mode 100644 index 0000000000..c22f2d7195 --- /dev/null +++ b/system/xen/patches/xsa179-qemuu-4.6-0005-vga-make-sure-vga-register-setup-for-vbe-stays-intac.patch @@ -0,0 +1,75 @@ +From 92456c0c361d5da858d544647c6246ec78ed922b Mon Sep 17 00:00:00 2001 +From: Gerd Hoffmann <kraxel@redhat.com> +Date: Tue, 26 Apr 2016 14:48:06 +0200 +Subject: [PATCH 5/5] vga: make sure vga register setup for vbe stays intact + (CVE-2016-3712). + +Call vbe_update_vgaregs() when the guest touches GFX, SEQ or CRT +registers, to make sure the vga registers will always have the +values needed by vbe mode. This makes sure the sanity checks +applied by vbe_fixup_regs() are effective. + +Without this guests can muck with shift_control, can turn on planar +vga modes or text mode emulation while VBE is active, making qemu +take code paths meant for CGA compatibility, but with the very +large display widths and heigts settable using VBE registers. + +Which is good for one or another buffer overflow. Not that +critical as they typically read overflows happening somewhere +in the display code. So guests can DoS by crashing qemu with a +segfault, but it is probably not possible to break out of the VM. + +Fixes: CVE-2016-3712 +Reported-by: Zuozhi Fzz <zuozhi.fzz@alibaba-inc.com> +Reported-by: P J P <ppandit@redhat.com> +Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> +Signed-off-by: Stefano Stabellini <sstabellini@kernel.org> +--- + hw/display/vga.c | 6 ++++++ + 1 file changed, 6 insertions(+) + +diff --git a/hw/display/vga.c b/hw/display/vga.c +index 3739758..e7be97e 100644 +--- a/hw/display/vga.c ++++ b/hw/display/vga.c +@@ -140,6 +140,8 @@ static uint32_t expand4[256]; + static uint16_t expand2[256]; + static uint8_t expand4to8[16]; + ++static void vbe_update_vgaregs(VGACommonState *s); ++ + static inline bool vbe_enabled(VGACommonState *s) + { + return s->vbe_regs[VBE_DISPI_INDEX_ENABLE] & VBE_DISPI_ENABLED; +@@ -483,6 +485,7 @@ void vga_ioport_write(void *opaque, uint32_t addr, uint32_t val) + printf("vga: write SR%x = 0x%02x\n", s->sr_index, val); + #endif + s->sr[s->sr_index] = val & sr_mask[s->sr_index]; ++ vbe_update_vgaregs(s); + if (s->sr_index == VGA_SEQ_CLOCK_MODE) { + s->update_retrace_info(s); + } +@@ -514,6 +517,7 @@ void vga_ioport_write(void *opaque, uint32_t addr, uint32_t val) + printf("vga: write GR%x = 0x%02x\n", s->gr_index, val); + #endif + s->gr[s->gr_index] = val & gr_mask[s->gr_index]; ++ vbe_update_vgaregs(s); + vga_update_memory_access(s); + break; + case VGA_CRT_IM: +@@ -532,10 +536,12 @@ void vga_ioport_write(void *opaque, uint32_t addr, uint32_t val) + if (s->cr_index == VGA_CRTC_OVERFLOW) { + s->cr[VGA_CRTC_OVERFLOW] = (s->cr[VGA_CRTC_OVERFLOW] & ~0x10) | + (val & 0x10); ++ vbe_update_vgaregs(s); + } + return; + } + s->cr[s->cr_index] = val; ++ vbe_update_vgaregs(s); + + switch(s->cr_index) { + case VGA_CRTC_H_TOTAL: +-- +1.9.1 + |