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KVM: fix KVM_CLEAR_DIRTY_LOG for memory slots of unaligned size

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If a memory slot's size is not a multiple of 64 pages (256K), then
the KVM_CLEAR_DIRTY_LOG API is unusable: clearing the final 64 pages
either requires the requested page range to go beyond memslot->npages,
or requires log->num_pages to be unaligned, and kvm_clear_dirty_log_protect
requires log->num_pages to be both in range and aligned.

To allow this case, allow log->num_pages not to be a multiple of 64 if
it ends exactly on the last page of the slot.

Reported-by: Peter Xu <peterx@redhat.com>
Fixes: 98938aa8ed ("KVM: validate userspace input in kvm_clear_dirty_log_protect()", 2019-01-02)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini
2019-04-17 15:28:44 +02:00
parent 0699c64a4b
commit 76d58e0f07
3 changed files with 13 additions and 8 deletions
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7
virt/kvm/kvm_main.c
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@@ -1240,7 +1240,7 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
return -EINVAL;
if ((log->first_page & 63) || (log->num_pages & 63))
if (log->first_page & 63)
return -EINVAL;
slots = __kvm_memslots(kvm, as_id);
@@ -1253,8 +1253,9 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
n = kvm_dirty_bitmap_bytes(memslot);
if (log->first_page > memslot->npages ||
log->num_pages > memslot->npages - log->first_page)
return -EINVAL;
log->num_pages > memslot->npages - log->first_page ||
(log->num_pages < memslot->npages - log->first_page && (log->num_pages & 63)))
return -EINVAL;
*flush = false;
dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);