asus-wmi: Restrict debugfs interface when the kernel is locked down

We have no way of validating what all of the Asus WMI methods do on a given
machine - and there's a risk that some will allow hardware state to be
manipulated in such a way that arbitrary code can be executed in the
kernel, circumventing module loading restrictions.  Prevent that if the
kernel is locked down.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0052-asus-wmi-Restrict-debugfs-interface-when-the-kernel-.patch

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 6c7d86074b38409ca726e28d069c39741d795eac..57b82cbc9a6bf8e8263ecde61e8ec2d4c3ed6f77 100644 (file)
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1905,6 +1905,9 @@ static int show_dsts(struct seq_file *m, void *data)
        int err;
        u32 retval = -1;
 
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
 
        if (err < 0)
@@ -1921,6 +1924,9 @@ static int show_devs(struct seq_file *m, void *data)
        int err;
        u32 retval = -1;
 
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
                                    &retval);
 
@@ -1945,6 +1951,9 @@ static int show_call(struct seq_file *m, void *data)
        union acpi_object *obj;
        acpi_status status;
 
+       if (kernel_is_locked_down())
+               return -EPERM;
+
        status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
                                     1, asus->debug.method_id,
                                     &input, &output);