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 390e664ec1c7..6bee6af8d8e1 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 fd488ad4263a..a1cb5afe6801 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;