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ssd0323: fix buffer overun on invalid state load

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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>
This commit is contained in:
Michael S. Tsirkin 2014-04-03 19:52:05 +03:00 committed by Juan Quintela
parent caa881abe0
commit ead7a57df3
1 changed files with 24 additions and 0 deletions
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24
hw/display/ssd0323.c
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@ -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);