Re: [PATCH] kvm: allocate correct size for dirty bitmap

[Marcelo Tosatti]

On Wed, Sep 23, 2009 at 04:13:18PM -0600, Bruce Rogers wrote:
 The dirty bitmap copied out to userspace is stored in a long array, and gets 
 copied out to userspace accordingly.  This patch accounts for that correctly. 
  Currently I'm seeing kvm crashing due to writing beyond the end of the 
 alloc'd dirty bitmap memory, because the buffer has the wrong size.
 
 Signed-off-by: Bruce Rogers 
 ---
  qemu-kvm.c |2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)
 
 diff --git a/qemu-kvm.c b/qemu-kvm.c
 index 6511cb6..ee5db76 100644
 --- a/qemu-kvm.c
 +++ b/qemu-kvm.c
 @@ -702,7 +702,7 @@ int kvm_get_dirty_pages_range(kvm_context_t kvm, unsigned 
 long phys_addr,
  for (i = 0; i  KVM_MAX_NUM_MEM_REGIONS; ++i) {
  if ((slots[i].len  (uint64_t) slots[i].phys_addr = phys_addr)
   ((uint64_t) slots[i].phys_addr + slots[i].len = end_addr)) {
 -buf = qemu_malloc((slots[i].len / 4096 + 7) / 8 + 2);
 +buf = qemu_malloc(BITMAP_SIZE(slots[i].len));
  r = kvm_get_map(kvm, KVM_GET_DIRTY_LOG, i, buf);
  if (r) {
  qemu_free(buf);

Applied, thanks.

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[PATCH] kvm: allocate correct size for dirty bitmap

[Bruce Rogers]

The dirty bitmap copied out to userspace is stored in a long array, and gets 
copied out to userspace accordingly.  This patch accounts for that correctly.  
Currently I'm seeing kvm crashing due to writing beyond the end of the alloc'd 
dirty bitmap memory, because the buffer has the wrong size.

Signed-off-by: Bruce Rogers 
---
 qemu-kvm.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/qemu-kvm.c b/qemu-kvm.c
index 6511cb6..ee5db76 100644
--- a/qemu-kvm.c
+++ b/qemu-kvm.c
@@ -702,7 +702,7 @@ int kvm_get_dirty_pages_range(kvm_context_t kvm, unsigned 
long phys_addr,
 for (i = 0; i  KVM_MAX_NUM_MEM_REGIONS; ++i) {
 if ((slots[i].len  (uint64_t) slots[i].phys_addr = phys_addr)
  ((uint64_t) slots[i].phys_addr + slots[i].len = end_addr)) {
-buf = qemu_malloc((slots[i].len / 4096 + 7) / 8 + 2);
+buf = qemu_malloc(BITMAP_SIZE(slots[i].len));
 r = kvm_get_map(kvm, KVM_GET_DIRTY_LOG, i, buf);
 if (r) {
 qemu_free(buf);


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