block: vpc - prevent overflow

Changes:

v3: check for INT_MAX / 4 as well, and use ROUND_UP (Thanks Max)

v2 now also checks that Max Table Entries is < SIZE_MAX / 4 (Thanks Stefan)

This series fixes a bug found by Richard Jones.

When we allocate the pagetable based on max_table_entries, we multiply the max table entry value by 4 to accomodate a table of 32-bit integers. However, max_table_entries is a uint32_t, and the VPC driver accepts ranges for that entry over 0x40000000. So during this allocation:

s->pagetable = qemu_try_blockalign(bs->file, s->max_table_entries * 4);

The size arg overflows, allocating significantly less memory than expected.

Since qemu_try_blockalign() size argument is size_t, cast the multiplication correctly to prevent overflow.

The value of "max_table_entries * 4" is used elsewhere in the code as well, so store the correct value for use in all those cases.

Jeff Cody (2):
block: vpc - prevent overflow if max_table_entries >= 0x40000000
block: qemu-iotests - add check for multiplication overflow in vpc

 block/vpc.c                                   |  18 +++++++--
 tests/qemu-iotests/135                        |  54 ++++++++++++++++++++++++++
 tests/qemu-iotests/135.out                    |   5 +++
 tests/qemu-iotests/group                      |   1 +
 tests/qemu-iotests/sample_images/afl5.img.bz2 | Bin 0 -> 175 bytes
 5 files changed, 74 insertions(+), 4 deletions(-)
 create mode 100755 tests/qemu-iotests/135
 create mode 100644 tests/qemu-iotests/135.out
 create mode 100644 tests/qemu-iotests/sample_images/afl5.img.bz2

1.9.3