Merge tag 'iwlwifi-fixes-for-kalle-2014-12-18' of git://git.kernel.org/pub/scm/linux...

[cascardo/linux.git] / drivers / base / devcoredump.c

diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
index 96614b0..1bd120a 100644 (file)
--- a/drivers/base/devcoredump.c
+++ b/drivers/base/devcoredump.c
@@ -31,6 +31,11 @@
 #include <linux/fs.h>
 #include <linux/workqueue.h>
 
+static struct class devcd_class;
+
+/* global disable flag, for security purposes */
+static bool devcd_disabled;
+
 /* if data isn't read by userspace after 5 minutes then delete it */
 #define DEVCD_TIMEOUT  (HZ * 60 * 5)
 
@@ -121,11 +126,51 @@ static const struct attribute_group *devcd_dev_groups[] = {
        &devcd_dev_group, NULL,
 };
 
+static int devcd_free(struct device *dev, void *data)
+{
+       struct devcd_entry *devcd = dev_to_devcd(dev);
+
+       flush_delayed_work(&devcd->del_wk);
+       return 0;
+}
+
+static ssize_t disabled_show(struct class *class, struct class_attribute *attr,
+                            char *buf)
+{
+       return sprintf(buf, "%d\n", devcd_disabled);
+}
+
+static ssize_t disabled_store(struct class *class, struct class_attribute *attr,
+                             const char *buf, size_t count)
+{
+       long tmp = simple_strtol(buf, NULL, 10);
+
+       /*
+        * This essentially makes the attribute write-once, since you can't
+        * go back to not having it disabled. This is intentional, it serves
+        * as a system lockdown feature.
+        */
+       if (tmp != 1)
+               return -EINVAL;
+
+       devcd_disabled = true;
+
+       class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
+
+       return count;
+}
+
+static struct class_attribute devcd_class_attrs[] = {
+       __ATTR_RW(disabled),
+       __ATTR_NULL
+};
+
 static struct class devcd_class = {
        .name           = "devcoredump",
        .owner          = THIS_MODULE,
        .dev_release    = devcd_dev_release,
        .dev_groups     = devcd_dev_groups,
+       .class_attrs    = devcd_class_attrs,
 };
 
 static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
@@ -192,6 +237,9 @@ void dev_coredumpm(struct device *dev, struct module *owner,
        struct devcd_entry *devcd;
        struct device *existing;
 
+       if (devcd_disabled)
+               goto free;
+
        existing = class_find_device(&devcd_class, NULL, dev,
                                     devcd_match_failing);
        if (existing) {
@@ -249,14 +297,6 @@ static int __init devcoredump_init(void)
 }
 __initcall(devcoredump_init);
 
-static int devcd_free(struct device *dev, void *data)
-{
-       struct devcd_entry *devcd = dev_to_devcd(dev);
-
-       flush_delayed_work(&devcd->del_wk);
-       return 0;
-}
-
 static void __exit devcoredump_exit(void)
 {
        class_for_each_device(&devcd_class, NULL, NULL, devcd_free);