From: Paolo Bonzini pbonzini@redhat.com

[ Upstream commit 76d58e0f07ec203bbdfcaabd9a9fc10a5a3ed5ea ]

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: 98938aa8edd6 ("KVM: validate userspace input in kvm_clear_dirty_log_protect()", 2019-01-02) Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/virtual/kvm/api.txt | 5 +++-- tools/testing/selftests/kvm/dirty_log_test.c | 9 ++++++--- virt/kvm/kvm_main.c | 7 ++++--- 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index ba8927c0d45c4..a1b8e6d92298c 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -3790,8 +3790,9 @@ 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). diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c index 4715cfba20dce..93f99c6b7d79e 100644 --- a/tools/testing/selftests/kvm/dirty_log_test.c +++ b/tools/testing/selftests/kvm/dirty_log_test.c @@ -288,8 +288,11 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations, #endif max_gfn = (1ul << (guest_pa_bits - guest_page_shift)) - 1; guest_page_size = (1ul << guest_page_shift); - /* 1G of guest page sized pages */ - guest_num_pages = (1ul << (30 - guest_page_shift)); + /* + * A little more than 1G of guest page sized pages. Cover the + * case where the size is not aligned to 64 pages. + */ + guest_num_pages = (1ul << (30 - guest_page_shift)) + 3; host_page_size = getpagesize(); host_num_pages = (guest_num_pages * guest_page_size) / host_page_size + !!((guest_num_pages * guest_page_size) % host_page_size); @@ -359,7 +362,7 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations, kvm_vm_get_dirty_log(vm, TEST_MEM_SLOT_INDEX, bmap); #ifdef USE_CLEAR_DIRTY_LOG kvm_vm_clear_dirty_log(vm, TEST_MEM_SLOT_INDEX, bmap, 0, - DIV_ROUND_UP(host_num_pages, 64) * 64); + host_num_pages); #endif vm_dirty_log_verify(bmap); iteration++; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index b4f2d892a1d36..c9b102e65a3a7 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1241,7 +1241,7 @@ 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); @@ -1254,8 +1254,9 @@ 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);