driver core: add uid and gid to devtmpfs

Some drivers want to tell userspace what uid and gid should be used for
their device nodes, so allow that information to percolate through the
driver core to userspace in order to make this happen.  This means that
some systems (i.e.  Android and friends) will not need to even run a
udev-like daemon for their device node manager and can just rely in
devtmpfs fully, reducing their footprint even more.

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

2 files changed, 30 insertions, 14 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index a7391a30cb2..8a428b51089 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -283,15 +283,21 @@ static int dev_uevent(struct kset *kset, struct kobject *kobj,
 		const char *tmp;
 		const char *name;
 		umode_t mode = 0;
+		uid_t uid = 0;
+		gid_t gid = 0;
 
 		add_uevent_var(env, "MAJOR=%u", MAJOR(dev->devt));
 		add_uevent_var(env, "MINOR=%u", MINOR(dev->devt));
-		name = device_get_devnode(dev, &mode, &tmp);
+		name = device_get_devnode(dev, &mode, &uid, &gid, &tmp);
 		if (name) {
 			add_uevent_var(env, "DEVNAME=%s", name);
-			kfree(tmp);
 			if (mode)
 				add_uevent_var(env, "DEVMODE=%#o", mode & 0777);
+			if (uid)
+				add_uevent_var(env, "DEVUID=%u", uid);
+			if (gid)
+				add_uevent_var(env, "DEVGID=%u", gid);
+			kfree(tmp);
 		}
 	}
 
@@ -1281,6 +1287,8 @@ static struct device *next_device(struct klist_iter *i)
  * device_get_devnode - path of device node file
  * @dev: device
  * @mode: returned file access mode
+ * @uid: returned file owner
+ * @gid: returned file group
  * @tmp: possibly allocated string
  *
  * Return the relative path of a possible device node.
@@ -1289,7 +1297,8 @@ static struct device *next_device(struct klist_iter *i)
  * freed by the caller.
  */
 const char *device_get_devnode(struct device *dev,
-			       umode_t *mode, const char **tmp)
+			       umode_t *mode, uid_t *uid, gid_t *gid,
+			       const char **tmp)
 {
 	char *s;
 
@@ -1297,7 +1306,7 @@ const char *device_get_devnode(struct device *dev,
 
 	/* the device type may provide a specific name */
 	if (dev->type && dev->type->devnode)
-		*tmp = dev->type->devnode(dev, mode);
+		*tmp = dev->type->devnode(dev, mode, uid, gid);
 	if (*tmp)
 		return *tmp;
 
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 01fc5b07f95..fda52563677 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -41,6 +41,8 @@ static struct req {
 	int err;
 	const char *name;
 	umode_t mode;	/* 0 => delete */
+	uid_t uid;
+	gid_t gid;
 	struct device *dev;
 } *requests;
 
@@ -85,7 +87,9 @@ int devtmpfs_create_node(struct device *dev)
 		return 0;
 
 	req.mode = 0;
-	req.name = device_get_devnode(dev, &req.mode, &tmp);
+	req.uid = 0;
+	req.gid = 0;
+	req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
 	if (!req.name)
 		return -ENOMEM;
 
@@ -121,7 +125,7 @@ int devtmpfs_delete_node(struct device *dev)
 	if (!thread)
 		return 0;
 
-	req.name = device_get_devnode(dev, NULL, &tmp);
+	req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
 	if (!req.name)
 		return -ENOMEM;
 
@@ -187,7 +191,8 @@ static int create_path(const char *nodepath)
 	return err;
 }
 
-static int handle_create(const char *nodename, umode_t mode, struct device *dev)
+static int handle_create(const char *nodename, umode_t mode, uid_t uid,
+			 gid_t gid, struct device *dev)
 {
 	struct dentry *dentry;
 	struct path path;
@@ -201,14 +206,14 @@ static int handle_create(const char *nodename, umode_t mode, struct device *dev)
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	err = vfs_mknod(path.dentry->d_inode,
-			dentry, mode, dev->devt);
+	err = vfs_mknod(path.dentry->d_inode, dentry, mode, dev->devt);
 	if (!err) {
 		struct iattr newattrs;
 
-		/* fixup possibly umasked mode */
 		newattrs.ia_mode = mode;
-		newattrs.ia_valid = ATTR_MODE;
+		newattrs.ia_uid = uid;
+		newattrs.ia_gid = gid;
+		newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID;
 		mutex_lock(&dentry->d_inode->i_mutex);
 		notify_change(dentry, &newattrs);
 		mutex_unlock(&dentry->d_inode->i_mutex);
@@ -358,10 +363,11 @@ int devtmpfs_mount(const char *mntdir)
 
 static DECLARE_COMPLETION(setup_done);
 
-static int handle(const char *name, umode_t mode, struct device *dev)
+static int handle(const char *name, umode_t mode, uid_t uid, gid_t gid,
+		  struct device *dev)
 {
 	if (mode)
-		return handle_create(name, mode, dev);
+		return handle_create(name, mode, uid, gid, dev);
 	else
 		return handle_remove(name, dev);
 }
@@ -387,7 +393,8 @@ static int devtmpfsd(void *p)
 			spin_unlock(&req_lock);
 			while (req) {
 				struct req *next = req->next;
-				req->err = handle(req->name, req->mode, req->dev);
+				req->err = handle(req->name, req->mode,
+						  req->uid, req->gid, req->dev);
 				complete(&req->done);
 				req = next;
 			}