KVM: remove the usage of the mmap_sem for the protection of the memory slots.

This patch replaces the mmap_sem lock for the memory slots with a new
kvm private lock, it is needed beacuse untill now there were cases where
kvm accesses user memory while holding the mmap semaphore.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 32fbf8006969..b2e12893e3f4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -169,6 +169,7 @@ static struct kvm *kvm_create_vm(void)
         kvm_io_bus_init(&kvm->pio_bus);
         mutex_init(&kvm->lock);
         kvm_io_bus_init(&kvm->mmio_bus);
+        init_rwsem(&kvm->slots_lock);
         spin_lock(&kvm_lock);
         list_add(&kvm->vm_list, &vm_list);
         spin_unlock(&kvm_lock);
@@ -339,9 +340,9 @@ int kvm_set_memory_region(struct kvm *kvm,
 {
         int r;
 
-        down_write(&current->mm->mmap_sem);
+        down_write(&kvm->slots_lock);
         r = __kvm_set_memory_region(kvm, mem, user_alloc);
-        up_write(&current->mm->mmap_sem);
+        up_write(&kvm->slots_lock);
         return r;
 }
 EXPORT_SYMBOL_GPL(kvm_set_memory_region);