KVM: limit the number of pages per memory slot
This patch limits the number of pages per memory slot to make
us free from extra care about type issues.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 169d077..5583063 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -105,6 +105,12 @@
struct kvm_vcpu_arch arch;
};
+/*
+ * Some of the bitops functions do not support too long bitmaps.
+ * This number must be determined not to exceed such limits.
+ */
+#define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1)
+
struct kvm_memory_slot {
gfn_t base_gfn;
unsigned long npages;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 55a5d48..d6351a3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -557,6 +557,10 @@
base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
npages = mem->memory_size >> PAGE_SHIFT;
+ r = -EINVAL;
+ if (npages > KVM_MEM_MAX_NR_PAGES)
+ goto out;
+
if (!npages)
mem->flags &= ~KVM_MEM_LOG_DIRTY_PAGES;
@@ -1187,13 +1191,10 @@
memslot = gfn_to_memslot_unaliased(kvm, gfn);
if (memslot && memslot->dirty_bitmap) {
unsigned long rel_gfn = gfn - memslot->base_gfn;
- unsigned long *p = memslot->dirty_bitmap +
- rel_gfn / BITS_PER_LONG;
- int offset = rel_gfn % BITS_PER_LONG;
/* avoid RMW */
- if (!generic_test_le_bit(offset, p))
- generic___set_le_bit(offset, p);
+ if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap))
+ generic___set_le_bit(rel_gfn, memslot->dirty_bitmap);
}
}