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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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5
Documentation/virtual/kvm/api.txt
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@@ -3830,8 +3830,9 @@ The ioctl clears the dirty status of pages in a memory slot, according to
the bitmap that is passed in struct kvm_clear_dirty_log's dirty_bitmap
field. Bit 0 of the bitmap corresponds to page "first_page" in the
memory slot, and num_pages is the size in bits of the input bitmap.
Both first_page and num_pages must be a multiple of 64. For each bit
that is set in the input bitmap, the corresponding page is marked "clean"
first_page must be a multiple of 64; num_pages must also be a multiple of
64 unless first_page + num_pages is the size of the memory slot. For each
bit that is set in the input bitmap, the corresponding page is marked "clean"
in KVM's dirty bitmap, and dirty tracking is re-enabled for that page
(for example via write-protection, or by clearing the dirty bit in
a page table entry).