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From 6dbbf055148c6f1b7d8a3251a65bd6f3d1e1f622 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@linaro.org>
Date: Mon, 28 Nov 2022 21:27:40 +0100
Subject: [PATCH] hw/display/qxl: Avoid buffer overrun in qxl_phys2virt
(CVE-2022-4144)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Have qxl_get_check_slot_offset() return false if the requested
buffer size does not fit within the slot memory region.
Similarly qxl_phys2virt() now returns NULL in such case, and
qxl_dirty_one_surface() aborts.
This avoids buffer overrun in the host pointer returned by
memory_region_get_ram_ptr().
Fixes: CVE-2022-4144 (out-of-bounds read)
Reported-by: Wenxu Yin (@awxylitol)
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1336
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20221128202741.4945-5-philmd@linaro.org>
Upstream-Status: Backport [https://gitlab.com/qemu-project/qemu/-/commit/6dbbf055148c6f1b7d8a3251a65bd6f3d1e1f622]
CVE: CVE-2022-4144
Comments: Deleted patch hunk in qxl.h,as it contains change
in comments which is not present in current version of qemu.
Signed-off-by: Hitendra Prajapati <hprajapati@mvista.com>
---
hw/display/qxl.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/hw/display/qxl.c b/hw/display/qxl.c
index cd7eb39d..6bc8385b 100644
--- a/hw/display/qxl.c
+++ b/hw/display/qxl.c
@@ -1440,11 +1440,13 @@ static void qxl_reset_surfaces(PCIQXLDevice *d)
/* can be also called from spice server thread context */
static bool qxl_get_check_slot_offset(PCIQXLDevice *qxl, QXLPHYSICAL pqxl,
- uint32_t *s, uint64_t *o)
+ uint32_t *s, uint64_t *o,
+ size_t size_requested)
{
uint64_t phys = le64_to_cpu(pqxl);
uint32_t slot = (phys >> (64 - 8)) & 0xff;
uint64_t offset = phys & 0xffffffffffff;
+ uint64_t size_available;
if (slot >= NUM_MEMSLOTS) {
qxl_set_guest_bug(qxl, "slot too large %d >= %d", slot,
@@ -1468,6 +1470,23 @@ static bool qxl_get_check_slot_offset(PCIQXLDevice *qxl, QXLPHYSICAL pqxl,
slot, offset, qxl->guest_slots[slot].size);
return false;
}
+ size_available = memory_region_size(qxl->guest_slots[slot].mr);
+ if (qxl->guest_slots[slot].offset + offset >= size_available) {
+ qxl_set_guest_bug(qxl,
+ "slot %d offset %"PRIu64" > region size %"PRIu64"\n",
+ slot, qxl->guest_slots[slot].offset + offset,
+ size_available);
+ return false;
+ }
+ size_available -= qxl->guest_slots[slot].offset + offset;
+ if (size_requested > size_available) {
+ qxl_set_guest_bug(qxl,
+ "slot %d offset %"PRIu64" size %zu: "
+ "overrun by %"PRIu64" bytes\n",
+ slot, offset, size_requested,
+ size_requested - size_available);
+ return false;
+ }
*s = slot;
*o = offset;
@@ -1486,7 +1505,7 @@ void *qxl_phys2virt(PCIQXLDevice *qxl, QXLPHYSICAL pqxl, int group_id)
offset = le64_to_cpu(pqxl) & 0xffffffffffff;
return (void *)(intptr_t)offset;
case MEMSLOT_GROUP_GUEST:
- if (!qxl_get_check_slot_offset(qxl, pqxl, &slot, &offset)) {
+ if (!qxl_get_check_slot_offset(qxl, pqxl, &slot, &offset, size)) {
return NULL;
}
ptr = memory_region_get_ram_ptr(qxl->guest_slots[slot].mr);
@@ -1944,9 +1963,9 @@ static void qxl_dirty_one_surface(PCIQXLDevice *qxl, QXLPHYSICAL pqxl,
uint32_t slot;
bool rc;
- rc = qxl_get_check_slot_offset(qxl, pqxl, &slot, &offset);
- assert(rc == true);
size = (uint64_t)height * abs(stride);
+ rc = qxl_get_check_slot_offset(qxl, pqxl, &slot, &offset, size);
+ assert(rc == true);
trace_qxl_surfaces_dirty(qxl->id, offset, size);
qxl_set_dirty(qxl->guest_slots[slot].mr,
qxl->guest_slots[slot].offset + offset,
--
2.25.1
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