Merge tag 'driver-core-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core update from Greg KH:
 "Here's the set of driver core patches for 3.19-rc1.

  They are dominated by the removal of the .owner field in platform
  drivers.  They touch a lot of files, but they are "simple" changes,
  just removing a line in a structure.

  Other than that, a few minor driver core and debugfs changes.  There
  are some ath9k patches coming in through this tree that have been
  acked by the wireless maintainers as they relied on the debugfs
  changes.

  Everything has been in linux-next for a while"

* tag 'driver-core-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (324 commits)
  Revert "ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries"
  fs: debugfs: add forward declaration for struct device type
  firmware class: Deletion of an unnecessary check before the function call "vunmap"
  firmware loader: fix hung task warning dump
  devcoredump: provide a one-way disable function
  device: Add dev_<level>_once variants
  ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries
  ath: use seq_file api for ath9k debugfs files
  debugfs: add helper function to create device related seq_file
  drivers/base: cacheinfo: remove noisy error boot message
  Revert "core: platform: add warning if driver has no owner"
  drivers: base: support cpu cache information interface to userspace via sysfs
  drivers: base: add cpu_device_create to support per-cpu devices
  topology: replace custom attribute macros with standard DEVICE_ATTR*
  cpumask: factor out show_cpumap into separate helper function
  driver core: Fix unbalanced device reference in drivers_probe
  driver core: fix race with userland in device_add()
  sysfs/kernfs: make read requests on pre-alloc files use the buffer.
  sysfs/kernfs: allow attributes to request write buffer be pre-allocated.
  fs: sysfs: return EGBIG on write if offset is larger than file size
  ...

1 files changed, 48 insertions, 8 deletions

diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
index 96614b04544c..1bd120a0b084 100644
--- 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);