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Subject[192/197] KVM: fix the handling of dirty bitmaps to avoid overflows
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>

(Cherry-picked from commit 87bf6e7de1134f48681fd2ce4b7c1ec45458cb6d)

Int is not long enough to store the size of a dirty bitmap.

This patch fixes this problem with the introduction of a wrapper
function to calculate the sizes of dirty bitmaps.

Note: in mark_page_dirty(), we have to consider the fact that
__set_bit() takes the offset as int, not long.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/ia64/kvm/kvm-ia64.c | 9 +++++----
arch/x86/kvm/x86.c | 4 ++--
include/linux/kvm_host.h | 5 +++++
virt/kvm/kvm_main.c | 13 ++++++++-----
4 files changed, 20 insertions(+), 11 deletions(-)
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1797,7 +1797,8 @@ static int kvm_ia64_sync_dirty_log(struc
{
struct kvm_memory_slot *memslot;
int r, i;
- long n, base;
+ long base;
+ unsigned long n;
unsigned long *dirty_bitmap = (unsigned long *)(kvm->arch.vm_base +
offsetof(struct kvm_vm_data, kvm_mem_dirty_log));

@@ -1810,7 +1811,7 @@ static int kvm_ia64_sync_dirty_log(struc
if (!memslot->dirty_bitmap)
goto out;

- n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+ n = kvm_dirty_bitmap_bytes(memslot);
base = memslot->base_gfn / BITS_PER_LONG;

for (i = 0; i < n/sizeof(long); ++i) {
@@ -1826,7 +1827,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kv
struct kvm_dirty_log *log)
{
int r;
- int n;
+ unsigned long n;
struct kvm_memory_slot *memslot;
int is_dirty = 0;

@@ -1844,7 +1845,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kv
if (is_dirty) {
kvm_flush_remote_tlbs(kvm);
memslot = &kvm->memslots[log->slot];
- n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+ n = kvm_dirty_bitmap_bytes(memslot);
memset(memslot->dirty_bitmap, 0, n);
}
r = 0;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2133,7 +2133,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kv
struct kvm_dirty_log *log)
{
int r;
- int n;
+ unsigned long n;
struct kvm_memory_slot *memslot;
int is_dirty = 0;

@@ -2149,7 +2149,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kv
kvm_mmu_slot_remove_write_access(kvm, log->slot);
spin_unlock(&kvm->mmu_lock);
memslot = &kvm->memslots[log->slot];
- n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+ n = kvm_dirty_bitmap_bytes(memslot);
memset(memslot->dirty_bitmap, 0, n);
}
r = 0;
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -116,6 +116,11 @@ struct kvm_memory_slot {
int user_alloc;
};

+static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)
+{
+ return ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+}
+
struct kvm_kernel_irq_routing_entry {
u32 gsi;
u32 type;
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1226,7 +1226,7 @@ skip_lpage:

/* Allocate page dirty bitmap if needed */
if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) {
- unsigned dirty_bytes = ALIGN(npages, BITS_PER_LONG) / 8;
+ unsigned long dirty_bytes = kvm_dirty_bitmap_bytes(&new);

new.dirty_bitmap = vmalloc(dirty_bytes);
if (!new.dirty_bitmap)
@@ -1309,7 +1309,7 @@ int kvm_get_dirty_log(struct kvm *kvm,
{
struct kvm_memory_slot *memslot;
int r, i;
- int n;
+ unsigned long n;
unsigned long any = 0;

r = -EINVAL;
@@ -1321,7 +1321,7 @@ int kvm_get_dirty_log(struct kvm *kvm,
if (!memslot->dirty_bitmap)
goto out;

- n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+ n = kvm_dirty_bitmap_bytes(memslot);

for (i = 0; !any && i < n/sizeof(long); ++i)
any = memslot->dirty_bitmap[i];
@@ -1663,10 +1663,13 @@ void mark_page_dirty(struct kvm *kvm, gf
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 (!test_bit(rel_gfn, memslot->dirty_bitmap))
- set_bit(rel_gfn, memslot->dirty_bitmap);
+ if (!test_bit(offset, p))
+ set_bit(offset, p);
}
}




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