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hw/display/qxl: Avoid buffer overrun in qxl_phys2virt (CVE-2022-4144)

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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>
This commit is contained in:
Philippe Mathieu-Daudé 2022-11-28 21:27:40 +01:00 committed by Stefan Hajnoczi
parent 8efec0ef8b
commit 6dbbf05514
2 changed files with 24 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
hw/display/qxl.c
View File

@ -1424,11 +1424,13 @@ 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,
@ -1452,6 +1454,23 @@ 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;
@ -1471,7 +1490,7 @@ 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);
@ -1937,9 +1956,9 @@ 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
hw/display/qxl.h
View File

@ -157,7 +157,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(PCIQXLDevice, PCI_QXL)
*
* Returns a host pointer to a buffer placed at offset @phys within the
* active slot @group_id of the PCI VGA RAM memory region associated with
* the @qxl device. If the slot is inactive, or the offset is out
* the @qxl device. If the slot is inactive, or the offset + size are out
* of the memory region, returns NULL.
*
* Use with care; by the time this function returns, the returned pointer is