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kvm: convert kvm.users_count from atomic_t to refcount_t

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refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Elena Reshetova
2017-02-20 13:06:21 +02:00
committed by Radim Krčmář
parent bba82fd756
commit e3736c3eb3
2 changed files with 6 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/kvm_host.h
+2 -1
View File
@@ -26,6 +26,7 @@
#include <linux/context_tracking.h> #include <linux/context_tracking.h>
#include <linux/irqbypass.h> #include <linux/irqbypass.h>
#include <linux/swait.h> #include <linux/swait.h>
#include <linux/refcount.h>
#include <asm/signal.h> #include <asm/signal.h>
#include <linux/kvm.h> #include <linux/kvm.h>
@@ -401,7 +402,7 @@ struct kvm {
#endif #endif
struct kvm_vm_stat stat; struct kvm_vm_stat stat;
struct kvm_arch arch; struct kvm_arch arch;
atomic_t users_count; refcount_t users_count;
#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
struct kvm_coalesced_mmio_ring *coalesced_mmio_ring; struct kvm_coalesced_mmio_ring *coalesced_mmio_ring;
spinlock_t ring_lock; spinlock_t ring_lock;
virt/kvm/kvm_main.c
+4 -4
View File
@@ -617,7 +617,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
mutex_init(&kvm->lock); mutex_init(&kvm->lock);
mutex_init(&kvm->irq_lock); mutex_init(&kvm->irq_lock);
mutex_init(&kvm->slots_lock); mutex_init(&kvm->slots_lock);
atomic_set(&kvm->users_count, 1); refcount_set(&kvm->users_count, 1);
INIT_LIST_HEAD(&kvm->devices); INIT_LIST_HEAD(&kvm->devices);
r = kvm_arch_init_vm(kvm, type); r = kvm_arch_init_vm(kvm, type);
@@ -747,13 +747,13 @@ static void kvm_destroy_vm(struct kvm *kvm)
void kvm_get_kvm(struct kvm *kvm) void kvm_get_kvm(struct kvm *kvm)
{ {
atomic_inc(&kvm->users_count); refcount_inc(&kvm->users_count);
} }
EXPORT_SYMBOL_GPL(kvm_get_kvm); EXPORT_SYMBOL_GPL(kvm_get_kvm);
void kvm_put_kvm(struct kvm *kvm) void kvm_put_kvm(struct kvm *kvm)
{ {
if (atomic_dec_and_test(&kvm->users_count)) if (refcount_dec_and_test(&kvm->users_count))
kvm_destroy_vm(kvm); kvm_destroy_vm(kvm);
} }
EXPORT_SYMBOL_GPL(kvm_put_kvm); EXPORT_SYMBOL_GPL(kvm_put_kvm);
@@ -3639,7 +3639,7 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
* To avoid the race between open and the removal of the debugfs * To avoid the race between open and the removal of the debugfs
* directory we test against the users count. * directory we test against the users count.
*/ */
if (!atomic_add_unless(&stat_data->kvm->users_count, 1, 0)) if (!refcount_inc_not_zero(&stat_data->kvm->users_count))
return -ENOENT; return -ENOENT;
if (simple_attr_open(inode, file, get, set, fmt)) { if (simple_attr_open(inode, file, get, set, fmt)) {