diff options
| -rw-r--r-- | kvm-all.c | 15 |
1 files changed, 14 insertions, 1 deletions
@@ -373,7 +373,20 @@ static int kvm_physical_sync_dirty_bitmap(target_phys_addr_t start_addr, break; } - size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS), HOST_LONG_BITS) / 8; + /* XXX bad kernel interface alert + * For dirty bitmap, kernel allocates array of size aligned to + * bits-per-long. But for case when the kernel is 64bits and + * the userspace is 32bits, userspace can't align to the same + * bits-per-long, since sizeof(long) is different between kernel + * and user space. This way, userspace will provide buffer which + * may be 4 bytes less than the kernel will use, resulting in + * userspace memory corruption (which is not detectable by valgrind + * too, in most cases). + * So for now, let's align to 64 instead of HOST_LONG_BITS here, in + * a hope that sizeof(long) wont become >8 any time soon. + */ + size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS), + /*HOST_LONG_BITS*/ 64) / 8; if (!d.dirty_bitmap) { d.dirty_bitmap = qemu_malloc(size); } else if (size > allocated_size) { |