From 4e1bfbe3a0a113fe3cf39336a9d7da4e8c2a21ea Mon Sep 17 00:00:00 2001

From: Jon Maloy <jmaloy@redhat.com>

Date: Mon, 5 Dec 2022 15:32:55 -0500

Subject: [PATCH 4/5] hw/display/qxl: Avoid buffer overrun in qxl_phys2virt

 (CVE-2022-4144)

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RH-Author: Jon Maloy <jmaloy@redhat.com>

RH-MergeRequest: 240: hw/display/qxl: Have qxl_log_command Return early if no log_cmd handler

RH-Bugzilla: 2148545

RH-Acked-by: Gerd Hoffmann <kraxel@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>

RH-Commit: [4/5] afe53f8d9b31c6fd8211fe172173151f3255e67c (jmaloy/jons-qemu-kvm)

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=2148545

CVE: CVE-2022-4144

Upstream: Merged

commit 6dbbf055148c6f1b7d8a3251a65bd6f3d1e1f622

Author: Philippe Mathieu-Daudé <philmd@linaro.org>

Date:   Mon Nov 28 21:27:40 2022 +0100

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

    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>

(cherry picked from commit 6dbbf055148c6f1b7d8a3251a65bd6f3d1e1f622)

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

---

 hw/display/qxl.c | 27 +++++++++++++++++++++++----

 hw/display/qxl.h |  2 +-

 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/hw/display/qxl.c b/hw/display/qxl.c

index aa9065183e..2a4b2d4158 100644

--- a/hw/display/qxl.c

+++ b/hw/display/qxl.c

@@ -1412,11 +1412,13 @@ 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,

@@ -1440,6 +1442,23 @@ 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;

@@ -1459,7 +1478,7 @@ 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);

@@ -1925,9 +1944,9 @@ 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,

diff --git a/hw/display/qxl.h b/hw/display/qxl.h

index c784315daa..89ca832cf9 100644

--- a/hw/display/qxl.h

+++ b/hw/display/qxl.h

@@ -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

-- 

2.37.3