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authorPaolo Bonzini <pbonzini@redhat.com>2019-04-17 15:28:44 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2019-04-30 21:22:15 +0200
commit76d58e0f07ec203bbdfcaabd9a9fc10a5a3ed5ea (patch)
tree8cf55a1022132806b63cceb24b286514c2210e34
parent0699c64a4be6e4a6137240379a1f82c752e663d8 (diff)
KVM: fix KVM_CLEAR_DIRTY_LOG for memory slots of unaligned size
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>
-rw-r--r--Documentation/virtual/kvm/api.txt5
-rw-r--r--tools/testing/selftests/kvm/dirty_log_test.c9
-rw-r--r--virt/kvm/kvm_main.c7
3 files changed, 13 insertions, 8 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 7f3ebc9e7cee..64b38dfcc243 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -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).
diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
index 4715cfba20dc..93f99c6b7d79 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 dc8edc97ba85..a704d1f9bd96 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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);