From 0cbd8c5754d6f56b53717e92353772777a799b87 Mon Sep 17 00:00:00 2001

From: "Michael S. Tsirkin" <mst@redhat.com>

Date: Thu, 3 Apr 2014 19:52:05 +0300

Subject: [PATCH] ssd0323: fix buffer overun on invalid state load

CVE-2013-4538

s->cmd_len used as index in ssd0323_transfer() to store 32-bit field.

Possible this field might then be supplied by guest to overwrite a

return addr somewhere. Same for row/col fields, which are indicies into

framebuffer array.

To fix validate after load.

Additionally, validate that the row/col_start/end are within bounds;

otherwise the guest can provoke an overrun by either setting the _end

field so large that the row++ increments just walk off the end of the

array, or by setting the _start value to something bogus and then

letting the "we hit end of row" logic reset row to row_start.

For completeness, validate mode as well.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Signed-off-by: Juan Quintela <quintela@redhat.com>

(cherry picked from commit ead7a57df37d2187813a121308213f41591bd811)

---

 hw/display/ssd0323.c | 24 ++++++++++++++++++++++++

 1 file changed, 24 insertions(+)

diff --git a/hw/display/ssd0323.c b/hw/display/ssd0323.c

index 971152e..9727007 100644

--- a/hw/display/ssd0323.c

+++ b/hw/display/ssd0323.c

@@ -312,18 +312,42 @@ static int ssd0323_load(QEMUFile *f, void *opaque, int version_id)

         return -EINVAL;

     s->cmd_len = qemu_get_be32(f);

+    if (s->cmd_len < 0 || s->cmd_len > ARRAY_SIZE(s->cmd_data)) {

+        return -EINVAL;

+    }

     s->cmd = qemu_get_be32(f);

     for (i = 0; i < 8; i++)

         s->cmd_data[i] = qemu_get_be32(f);

     s->row = qemu_get_be32(f);

+    if (s->row < 0 || s->row >= 80) {

+        return -EINVAL;

+    }

     s->row_start = qemu_get_be32(f);

+    if (s->row_start < 0 || s->row_start >= 80) {

+        return -EINVAL;

+    }

     s->row_end = qemu_get_be32(f);

+    if (s->row_end < 0 || s->row_end >= 80) {

+        return -EINVAL;

+    }

     s->col = qemu_get_be32(f);

+    if (s->col < 0 || s->col >= 64) {

+        return -EINVAL;

+    }

     s->col_start = qemu_get_be32(f);

+    if (s->col_start < 0 || s->col_start >= 64) {

+        return -EINVAL;

+    }

     s->col_end = qemu_get_be32(f);

+    if (s->col_end < 0 || s->col_end >= 64) {

+        return -EINVAL;

+    }

     s->redraw = qemu_get_be32(f);

     s->remap = qemu_get_be32(f);

     s->mode = qemu_get_be32(f);

+    if (s->mode != SSD0323_CMD && s->mode != SSD0323_DATA) {

+        return -EINVAL;

+    }

     qemu_get_buffer(f, s->framebuffer, sizeof(s->framebuffer));

     ss->cs = qemu_get_be32(f);