On Thu, Jun 25, 2015 at 11:05:20AM -0400, Jeff Cody wrote: > On Thu, Jun 25, 2015 at 03:28:35PM +0100, Stefan Hajnoczi wrote: > > On Wed, Jun 24, 2015 at 03:54:27PM -0400, Jeff Cody wrote: > > > @@ -269,7 +270,9 @@ static int vpc_open(BlockDriverState *bs, QDict > > > *options, int flags, > > > goto fail; > > > } > > > > > > - s->pagetable = qemu_try_blockalign(bs->file, > > > s->max_table_entries * 4); > > > + pagetable_size = (size_t) s->max_table_entries * 4; > > > + > > > + s->pagetable = qemu_try_blockalign(bs->file, pagetable_size); > > > > On 32-bit hosts size_t is 32-bit so the overflow hasn't been solved. > > > > Does it make sense to impose a limit on pagetable_size? > > Good point. Yes, it does. > > The VHD spec says that the "Max Table Entries" field should be equal > to the disk size / block size. I don't know if there are images out > there that treat that as ">= disk size / block size" rather than "==", > however. But if we assume max size of 2TB for a VHD disk, and a > minimal block size of 512 bytes, that would give us a > max_table_entries of 0x100000000, which exceeds 32 bits by itself. > > For pagetable_size to fit in a 32-bit, that means to support 2TB on a > 32-bit host in the current implementation, the minimum block size is > 4096. > > We could check during open / create that > (disk_size / block_size) * 4 < SIZE_MAX, and refuse to open if this is > not true (and also validate max_table_entries to fit in the same).
Sounds good.
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