KVM: Prevent kvm_init from corrupting debugfs structures
I'm seeing an oops condition when kvm-intel and kvm-amd are modprobe'd
during boot (say on an Intel system) and then rmmod'd:
# modprobe kvm-intel
kvm_init()
kvm_init_debug()
kvm_arch_init() <-- stores debugfs dentries internally
(success, etc)
# modprobe kvm-amd
kvm_init()
kvm_init_debug() <-- second initialization clobbers kvm's
internal pointers to dentries
kvm_arch_init()
kvm_exit_debug() <-- and frees them
# rmmod kvm-intel
kvm_exit()
kvm_exit_debug() <-- double free of debugfs files!
*BOOM*
If execution gets to the end of kvm_init(), then the calling module has been
established as the kvm provider. Move the debugfs initialization to the end of
the function, and remove the now-unnecessary call to kvm_exit_debug() from the
error path. That way we avoid trampling on the debugfs entries and freeing
them twice.
Cc: stable@kernel.org
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b7c78a4..7495ce3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2717,8 +2717,6 @@
int r;
int cpu;
- kvm_init_debug();
-
r = kvm_arch_init(opaque);
if (r)
goto out_fail;
@@ -2785,6 +2783,8 @@
kvm_preempt_ops.sched_in = kvm_sched_in;
kvm_preempt_ops.sched_out = kvm_sched_out;
+ kvm_init_debug();
+
return 0;
out_free:
@@ -2807,7 +2807,6 @@
out:
kvm_arch_exit();
out_fail:
- kvm_exit_debug();
return r;
}
EXPORT_SYMBOL_GPL(kvm_init);
@@ -2815,6 +2814,7 @@
void kvm_exit(void)
{
tracepoint_synchronize_unregister();
+ kvm_exit_debug();
misc_deregister(&kvm_dev);
kmem_cache_destroy(kvm_vcpu_cache);
sysdev_unregister(&kvm_sysdev);
@@ -2824,7 +2824,6 @@
on_each_cpu(hardware_disable, NULL, 1);
kvm_arch_hardware_unsetup();
kvm_arch_exit();
- kvm_exit_debug();
free_cpumask_var(cpus_hardware_enabled);
__free_page(bad_page);
}