Driver-Core: extend devnode callbacks to provide permissions

This allows subsytems to provide devtmpfs with non-default permissions
for the device node. Instead of the default mode of 0600, null, zero,
random, urandom, full, tty, ptmx now have a mode of 0666, which allows
non-privileged processes to access standard device nodes in case no
other userspace process applies the expected permissions.

This also fixes a wrong assignment in pktcdvd and a checkpatch.pl complain.

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 28 insertions, 15 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 390e664ec1c..6bee6af8d8e 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -166,13 +166,16 @@ static int dev_uevent(struct kset *kset, struct kobject *kobj,
 	if (MAJOR(dev->devt)) {
 		const char *tmp;
 		const char *name;
+		mode_t mode = 0;
 
 		add_uevent_var(env, "MAJOR=%u", MAJOR(dev->devt));
 		add_uevent_var(env, "MINOR=%u", MINOR(dev->devt));
-		name = device_get_nodename(dev, &tmp);
+		name = device_get_devnode(dev, &mode, &tmp);
 		if (name) {
 			add_uevent_var(env, "DEVNAME=%s", name);
 			kfree(tmp);
+			if (mode)
+				add_uevent_var(env, "DEVMODE=%#o", mode & 0777);
 		}
 	}
 
@@ -1148,8 +1151,9 @@ static struct device *next_device(struct klist_iter *i)
 }
 
 /**
- * device_get_nodename - path of device node file
+ * device_get_devnode - path of device node file
  * @dev: device
+ * @mode: returned file access mode
  * @tmp: possibly allocated string
  *
  * Return the relative path of a possible device node.
@@ -1157,21 +1161,22 @@ static struct device *next_device(struct klist_iter *i)
  * a name. This memory is returned in tmp and needs to be
  * freed by the caller.
  */
-const char *device_get_nodename(struct device *dev, const char **tmp)
+const char *device_get_devnode(struct device *dev,
+			       mode_t *mode, const char **tmp)
 {
 	char *s;
 
 	*tmp = NULL;
 
 	/* the device type may provide a specific name */
-	if (dev->type && dev->type->nodename)
-		*tmp = dev->type->nodename(dev);
+	if (dev->type && dev->type->devnode)
+		*tmp = dev->type->devnode(dev, mode);
 	if (*tmp)
 		return *tmp;
 
 	/* the class may provide a specific name */
-	if (dev->class && dev->class->nodename)
-		*tmp = dev->class->nodename(dev);
+	if (dev->class && dev->class->devnode)
+		*tmp = dev->class->devnode(dev, mode);
 	if (*tmp)
 		return *tmp;
 
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index fd488ad4263..a1cb5afe680 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -6,9 +6,10 @@
  * During bootup, before any driver core device is registered,
  * devtmpfs, a tmpfs-based filesystem is created. Every driver-core
  * device which requests a device node, will add a node in this
- * filesystem. The node is named after the the name of the device,
- * or the susbsytem can provide a custom name. All devices are
- * owned by root and have a mode of 0600.
+ * filesystem.
+ * By default, all devices are named after the the name of the
+ * device, owned by root and have a default mode of 0600. Subsystems
+ * can overwrite the default setting if needed.
  */
 
 #include <linux/kernel.h>
@@ -20,6 +21,7 @@
 #include <linux/fs.h>
 #include <linux/shmem_fs.h>
 #include <linux/cred.h>
+#include <linux/sched.h>
 #include <linux/init_task.h>
 
 static struct vfsmount *dev_mnt;
@@ -134,7 +136,7 @@ int devtmpfs_create_node(struct device *dev)
 	const char *tmp = NULL;
 	const char *nodename;
 	const struct cred *curr_cred;
-	mode_t mode;
+	mode_t mode = 0;
 	struct nameidata nd;
 	struct dentry *dentry;
 	int err;
@@ -142,14 +144,16 @@ int devtmpfs_create_node(struct device *dev)
 	if (!dev_mnt)
 		return 0;
 
-	nodename = device_get_nodename(dev, &tmp);
+	nodename = device_get_devnode(dev, &mode, &tmp);
 	if (!nodename)
 		return -ENOMEM;
 
+	if (mode == 0)
+		mode = 0600;
 	if (is_blockdev(dev))
-		mode = S_IFBLK|0600;
+		mode |= S_IFBLK;
 	else
-		mode = S_IFCHR|0600;
+		mode |= S_IFCHR;
 
 	curr_cred = override_creds(&init_cred);
 	err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
@@ -165,8 +169,12 @@ int devtmpfs_create_node(struct device *dev)
 
 	dentry = lookup_create(&nd, 0);
 	if (!IS_ERR(dentry)) {
+		int umask;
+
+		umask = sys_umask(0000);
 		err = vfs_mknod(nd.path.dentry->d_inode,
 				dentry, mode, dev->devt);
+		sys_umask(umask);
 		/* mark as kernel created inode */
 		if (!err)
 			dentry->d_inode->i_private = &dev_mnt;
@@ -271,7 +279,7 @@ int devtmpfs_delete_node(struct device *dev)
 	if (!dev_mnt)
 		return 0;
 
-	nodename = device_get_nodename(dev, &tmp);
+	nodename = device_get_devnode(dev, NULL, &tmp);
 	if (!nodename)
 		return -ENOMEM;