[OE-core] [PATCH][krogoth] qemu: CVE-2016-3710
Sona Sarmadi
sona.sarmadi at enea.com
Wed Sep 21 08:10:22 UTC 2016
Fixes an out-of-bounds read/write access flaw which was found
in the way QEMU's VGA emulation with VESA BIOS Extensions (VBE)
support performed read/write operations using I/O port methods.
A privileged guest user could use this flaw to execute arbitrary
code on the host with the privileges of the host's QEMU process.
Reference to pstream fix:
-------------------------
https://lists.gnu.org/archive/html/qemu-devel/2016-05/msg01197.html
References:
-----------
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-3710
http://www.openwall.com/lists/oss-security/2016/05/09/3
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-3710
Signed-off-by: Sona Sarmadi <sona.sarmadi at enea.com>
---
.../recipes-devtools/qemu/qemu/CVE-2016-3710.patch | 111 +++++++++++++++++++++
meta/recipes-devtools/qemu/qemu_2.5.0.bb | 1 +
2 files changed, 112 insertions(+)
create mode 100644 meta/recipes-devtools/qemu/qemu/CVE-2016-3710.patch
diff --git a/meta/recipes-devtools/qemu/qemu/CVE-2016-3710.patch b/meta/recipes-devtools/qemu/qemu/CVE-2016-3710.patch
new file mode 100644
index 0000000..48b9589
--- /dev/null
+++ b/meta/recipes-devtools/qemu/qemu/CVE-2016-3710.patch
@@ -0,0 +1,111 @@
+From 3bf1817079bb0d80c0d8a86a7c7dd0bfe90eb82e Mon Sep 17 00:00:00 2001
+From: Gerd Hoffmann <kraxel at redhat.com>
+Date: Tue, 26 Apr 2016 08:49:10 +0200
+Subject: [PATCH] vga: fix banked access bounds checking (CVE-2016-3710)
+
+vga allows banked access to video memory using the window at 0xa00000
+and it supports a different access modes with different address
+calculations.
+
+The VBE bochs extentions support banked access too, using the
+VBE_DISPI_INDEX_BANK register. The code tries to take the different
+address calculations into account and applies different limits to
+VBE_DISPI_INDEX_BANK depending on the current access mode.
+
+Which is probably effective in stopping misprogramming by accident.
+But from a security point of view completely useless as an attacker
+can easily change access modes after setting the bank register.
+
+Drop the bogus check, add range checks to vga_mem_{readb,writeb}
+instead.
+
+Upstream-Status: Backport [from v2.6.0-rc5~1^2~4
+commit: 3bf1817079bb0d80c0d8a86a7c7dd0bfe90eb82e]
+
+Fixes: CVE-2016-3710
+Reported-by: Qinghao Tang <luodalongde at gmail.com>
+Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
+Signed-off-by: Sona Sarmadi <sona.sarmadi at enea.com>
+---
+ hw/display/vga.c | 24 ++++++++++++++++++------
+ 1 file changed, 18 insertions(+), 6 deletions(-)
+
+diff --git a/hw/display/vga.c b/hw/display/vga.c
+index 657e9f1..b9191ca 100644
+--- a/hw/display/vga.c
++++ b/hw/display/vga.c
+@@ -179,6 +179,7 @@ static void vga_update_memory_access(VGACommonState *s)
+ size = 0x8000;
+ break;
+ }
++ assert(offset + size <= s->vram_size);
+ memory_region_init_alias(&s->chain4_alias, memory_region_owner(&s->vram),
+ "vga.chain4", &s->vram, offset, size);
+ memory_region_add_subregion_overlap(s->legacy_address_space, base,
+@@ -716,11 +717,7 @@ void vbe_ioport_write_data(void *opaque, uint32_t addr, uint32_t val)
+ vbe_fixup_regs(s);
+ break;
+ case VBE_DISPI_INDEX_BANK:
+- if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4) {
+- val &= (s->vbe_bank_mask >> 2);
+- } else {
+- val &= s->vbe_bank_mask;
+- }
++ val &= s->vbe_bank_mask;
+ s->vbe_regs[s->vbe_index] = val;
+ s->bank_offset = (val << 16);
+ vga_update_memory_access(s);
+@@ -819,13 +816,21 @@ uint32_t vga_mem_readb(VGACommonState *s, hwaddr addr)
+
+ if (s->sr[VGA_SEQ_MEMORY_MODE] & VGA_SR04_CHN_4M) {
+ /* chain 4 mode : simplest access */
++ assert(addr < s->vram_size);
+ ret = s->vram_ptr[addr];
+ } else if (s->gr[VGA_GFX_MODE] & 0x10) {
+ /* odd/even mode (aka text mode mapping) */
+ plane = (s->gr[VGA_GFX_PLANE_READ] & 2) | (addr & 1);
+- ret = s->vram_ptr[((addr & ~1) << 1) | plane];
++ addr = ((addr & ~1) << 1) | plane;
++ if (addr >= s->vram_size) {
++ return 0xff;
++ }
++ ret = s->vram_ptr[addr];
+ } else {
+ /* standard VGA latched access */
++ if (addr * sizeof(uint32_t) >= s->vram_size) {
++ return 0xff;
++ }
+ s->latch = ((uint32_t *)s->vram_ptr)[addr];
+
+ if (!(s->gr[VGA_GFX_MODE] & 0x08)) {
+@@ -882,6 +887,7 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)
+ plane = addr & 3;
+ mask = (1 << plane);
+ if (s->sr[VGA_SEQ_PLANE_WRITE] & mask) {
++ assert(addr < s->vram_size);
+ s->vram_ptr[addr] = val;
+ #ifdef DEBUG_VGA_MEM
+ printf("vga: chain4: [0x" TARGET_FMT_plx "]\n", addr);
+@@ -895,6 +901,9 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)
+ mask = (1 << plane);
+ if (s->sr[VGA_SEQ_PLANE_WRITE] & mask) {
+ addr = ((addr & ~1) << 1) | plane;
++ if (addr >= s->vram_size) {
++ return;
++ }
+ s->vram_ptr[addr] = val;
+ #ifdef DEBUG_VGA_MEM
+ printf("vga: odd/even: [0x" TARGET_FMT_plx "]\n", addr);
+@@ -968,6 +977,9 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)
+ mask = s->sr[VGA_SEQ_PLANE_WRITE];
+ s->plane_updated |= mask; /* only used to detect font change */
+ write_mask = mask16[mask];
++ if (addr * sizeof(uint32_t) >= s->vram_size) {
++ return;
++ }
+ ((uint32_t *)s->vram_ptr)[addr] =
+ (((uint32_t *)s->vram_ptr)[addr] & ~write_mask) |
+ (val & write_mask);
+--
+1.9.1
+
diff --git a/meta/recipes-devtools/qemu/qemu_2.5.0.bb b/meta/recipes-devtools/qemu/qemu_2.5.0.bb
index 03a6cbe..7651e9a 100644
--- a/meta/recipes-devtools/qemu/qemu_2.5.0.bb
+++ b/meta/recipes-devtools/qemu/qemu_2.5.0.bb
@@ -16,6 +16,7 @@ SRC_URI += "file://configure-fix-Darwin-target-detection.patch \
file://rng_remove_the_unused_request_cancellation_code.patch \
file://rng_move_request_queue_cleanup_from_RngEgd_to_RngBackend.patch \
file://CVE-2016-2858.patch \
+ file://CVE-2016-3710.patch \
"
SRC_URI_prepend = "http://wiki.qemu-project.org/download/${BP}.tar.bz2"
SRC_URI[md5sum] = "f469f2330bbe76e3e39db10e9ac4f8db"
--
1.9.1
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