1 files changed, 151 insertions, 131 deletions

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index 7496b10532aa..6a2185eb66c5 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -11,6 +11,7 @@
 #include <linux/kdev_t.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
+#include <linux/namei.h>
 #include <linux/magic.h>
 #include <linux/major.h>
 #include <linux/miscdevice.h>
@@ -20,6 +21,7 @@
 #include <linux/parser.h>
 #include <linux/radix-tree.h>
 #include <linux/sched.h>
+#include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/spinlock_types.h>
 #include <linux/stddef.h>
@@ -30,7 +32,7 @@
 #include <linux/xarray.h>
 #include <uapi/asm-generic/errno-base.h>
 #include <uapi/linux/android/binder.h>
-#include <uapi/linux/android/binder_ctl.h>
+#include <uapi/linux/android/binderfs.h>
 
 #include "binder_internal.h"
 
@@ -39,14 +41,32 @@
 #define INODE_OFFSET 3
 #define INTSTRLEN 21
 #define BINDERFS_MAX_MINOR (1U << MINORBITS)
-
-static struct vfsmount *binderfs_mnt;
+/* Ensure that the initial ipc namespace always has devices available. */
+#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4)
 
 static dev_t binderfs_dev;
 static DEFINE_MUTEX(binderfs_minors_mutex);
 static DEFINE_IDA(binderfs_minors);
 
 /**
+ * binderfs_mount_opts - mount options for binderfs
+ * @max: maximum number of allocatable binderfs binder devices
+ */
+struct binderfs_mount_opts {
+	int max;
+};
+
+enum {
+	Opt_max,
+	Opt_err
+};
+
+static const match_table_t tokens = {
+	{ Opt_max, "max=%d" },
+	{ Opt_err, NULL     }
+};
+
+/**
  * binderfs_info - information about a binderfs mount
  * @ipc_ns:         The ipc namespace the binderfs mount belongs to.
  * @control_dentry: This records the dentry of this binderfs mount
@@ -55,13 +75,16 @@ static DEFINE_IDA(binderfs_minors);
  *                  created.
  * @root_gid:       gid that needs to be used when a new binder device is
  *                  created.
+ * @mount_opts:     The mount options in use.
+ * @device_count:   The current number of allocated binder devices.
  */
 struct binderfs_info {
 	struct ipc_namespace *ipc_ns;
 	struct dentry *control_dentry;
 	kuid_t root_uid;
 	kgid_t root_gid;
-
+	struct binderfs_mount_opts mount_opts;
+	int device_count;
 };
 
 static inline struct binderfs_info *BINDERFS_I(const struct inode *inode)
@@ -84,7 +107,7 @@ bool is_binderfs_device(const struct inode *inode)
  * @userp:     buffer to copy information about new device for userspace to
  * @req:       struct binderfs_device as copied from userspace
  *
- * This function allocated a new binder_device and reserves a new minor
+ * This function allocates a new binder_device and reserves a new minor
  * number for it.
  * Minor numbers are limited and tracked globally in binderfs_minors. The
  * function will stash a struct binder_device for the specific binder
@@ -100,20 +123,34 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 					 struct binderfs_device *req)
 {
 	int minor, ret;
-	struct dentry *dentry, *dup, *root;
+	struct dentry *dentry, *root;
 	struct binder_device *device;
-	size_t name_len = BINDERFS_MAX_NAME + 1;
 	char *name = NULL;
+	size_t name_len;
 	struct inode *inode = NULL;
 	struct super_block *sb = ref_inode->i_sb;
 	struct binderfs_info *info = sb->s_fs_info;
+#if defined(CONFIG_IPC_NS)
+	bool use_reserve = (info->ipc_ns == &init_ipc_ns);
+#else
+	bool use_reserve = true;
+#endif
 
 	/* Reserve new minor number for the new device. */
 	mutex_lock(&binderfs_minors_mutex);
-	minor = ida_alloc_max(&binderfs_minors, BINDERFS_MAX_MINOR, GFP_KERNEL);
-	mutex_unlock(&binderfs_minors_mutex);
-	if (minor < 0)
+	if (++info->device_count <= info->mount_opts.max)
+		minor = ida_alloc_max(&binderfs_minors,
+				      use_reserve ? BINDERFS_MAX_MINOR :
+						    BINDERFS_MAX_MINOR_CAPPED,
+				      GFP_KERNEL);
+	else
+		minor = -ENOSPC;
+	if (minor < 0) {
+		--info->device_count;
+		mutex_unlock(&binderfs_minors_mutex);
 		return minor;
+	}
+	mutex_unlock(&binderfs_minors_mutex);
 
 	ret = -ENOMEM;
 	device = kzalloc(sizeof(*device), GFP_KERNEL);
@@ -132,12 +169,13 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 	inode->i_uid = info->root_uid;
 	inode->i_gid = info->root_gid;
 
-	name = kmalloc(name_len, GFP_KERNEL);
+	req->name[BINDERFS_MAX_NAME] = '\0'; /* NUL-terminate */
+	name_len = strlen(req->name);
+	/* Make sure to include terminating NUL byte */
+	name = kmemdup(req->name, name_len + 1, GFP_KERNEL);
 	if (!name)
 		goto err;
 
-	strscpy(name, req->name, name_len);
-
 	device->binderfs_inode = inode;
 	device->context.binder_context_mgr_uid = INVALID_UID;
 	device->context.name = name;
@@ -156,28 +194,25 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 
 	root = sb->s_root;
 	inode_lock(d_inode(root));
-	dentry = d_alloc_name(root, name);
-	if (!dentry) {
+
+	/* look it up */
+	dentry = lookup_one_len(name, root, name_len);
+	if (IS_ERR(dentry)) {
 		inode_unlock(d_inode(root));
-		ret = -ENOMEM;
+		ret = PTR_ERR(dentry);
 		goto err;
 	}
 
-	/* Verify that the name userspace gave us is not already in use. */
-	dup = d_lookup(root, &dentry->d_name);
-	if (dup) {
-		if (d_really_is_positive(dup)) {
-			dput(dup);
-			dput(dentry);
-			inode_unlock(d_inode(root));
-			ret = -EEXIST;
-			goto err;
-		}
-		dput(dup);
+	if (d_really_is_positive(dentry)) {
+		/* already exists */
+		dput(dentry);
+		inode_unlock(d_inode(root));
+		ret = -EEXIST;
+		goto err;
 	}
 
 	inode->i_private = device;
-	d_add(dentry, inode);
+	d_instantiate(dentry, inode);
 	fsnotify_create(root->d_inode, dentry);
 	inode_unlock(d_inode(root));
 
@@ -187,6 +222,7 @@ err:
 	kfree(name);
 	kfree(device);
 	mutex_lock(&binderfs_minors_mutex);
+	--info->device_count;
 	ida_free(&binderfs_minors, minor);
 	mutex_unlock(&binderfs_minors_mutex);
 	iput(inode);
@@ -232,6 +268,7 @@ static long binder_ctl_ioctl(struct file *file, unsigned int cmd,
 static void binderfs_evict_inode(struct inode *inode)
 {
 	struct binder_device *device = inode->i_private;
+	struct binderfs_info *info = BINDERFS_I(inode);
 
 	clear_inode(inode);
 
@@ -239,6 +276,7 @@ static void binderfs_evict_inode(struct inode *inode)
 		return;
 
 	mutex_lock(&binderfs_minors_mutex);
+	--info->device_count;
 	ida_free(&binderfs_minors, device->miscdev.minor);
 	mutex_unlock(&binderfs_minors_mutex);
 
@@ -246,43 +284,87 @@ static void binderfs_evict_inode(struct inode *inode)
 	kfree(device);
 }
 
+/**
+ * binderfs_parse_mount_opts - parse binderfs mount options
+ * @data: options to set (can be NULL in which case defaults are used)
+ */
+static int binderfs_parse_mount_opts(char *data,
+				     struct binderfs_mount_opts *opts)
+{
+	char *p;
+	opts->max = BINDERFS_MAX_MINOR;
+
+	while ((p = strsep(&data, ",")) != NULL) {
+		substring_t args[MAX_OPT_ARGS];
+		int token;
+		int max_devices;
+
+		if (!*p)
+			continue;
+
+		token = match_token(p, tokens, args);
+		switch (token) {
+		case Opt_max:
+			if (match_int(&args[0], &max_devices) ||
+			    (max_devices < 0 ||
+			     (max_devices > BINDERFS_MAX_MINOR)))
+				return -EINVAL;
+
+			opts->max = max_devices;
+			break;
+		default:
+			pr_err("Invalid mount options\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static int binderfs_remount(struct super_block *sb, int *flags, char *data)
+{
+	struct binderfs_info *info = sb->s_fs_info;
+	return binderfs_parse_mount_opts(data, &info->mount_opts);
+}
+
+static int binderfs_show_mount_opts(struct seq_file *seq, struct dentry *root)
+{
+	struct binderfs_info *info;
+
+	info = root->d_sb->s_fs_info;
+	if (info->mount_opts.max <= BINDERFS_MAX_MINOR)
+		seq_printf(seq, ",max=%d", info->mount_opts.max);
+
+	return 0;
+}
+
 static const struct super_operations binderfs_super_ops = {
-	.statfs = simple_statfs,
-	.evict_inode = binderfs_evict_inode,
+	.evict_inode    = binderfs_evict_inode,
+	.remount_fs	= binderfs_remount,
+	.show_options	= binderfs_show_mount_opts,
+	.statfs         = simple_statfs,
 };
 
+static inline bool is_binderfs_control_device(const struct dentry *dentry)
+{
+	struct binderfs_info *info = dentry->d_sb->s_fs_info;
+	return info->control_dentry == dentry;
+}
+
 static int binderfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 			   struct inode *new_dir, struct dentry *new_dentry,
 			   unsigned int flags)
 {
-	struct inode *inode = d_inode(old_dentry);
-
-	/* binderfs doesn't support directories. */
-	if (d_is_dir(old_dentry))
+	if (is_binderfs_control_device(old_dentry) ||
+	    is_binderfs_control_device(new_dentry))
 		return -EPERM;
 
-	if (flags & ~RENAME_NOREPLACE)
-		return -EINVAL;
-
-	if (!simple_empty(new_dentry))
-		return -ENOTEMPTY;
-
-	if (d_really_is_positive(new_dentry))
-		simple_unlink(new_dir, new_dentry);
-
-	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
-		new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
-
-	return 0;
+	return simple_rename(old_dir, old_dentry, new_dir, new_dentry, flags);
 }
 
 static int binderfs_unlink(struct inode *dir, struct dentry *dentry)
 {
-	/*
-	 * The control dentry is only ever touched during mount so checking it
-	 * here should not require us to take lock.
-	 */
-	if (BINDERFS_I(dir)->control_dentry == dentry)
+	if (is_binderfs_control_device(dentry))
 		return -EPERM;
 
 	return simple_unlink(dir, dentry);
@@ -318,8 +400,6 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 	if (!device)
 		return -ENOMEM;
 
-	inode_lock(d_inode(root));
-
 	/* If we have already created a binder-control node, return. */
 	if (info->control_dentry) {
 		ret = 0;
@@ -358,12 +438,10 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 	inode->i_private = device;
 	info->control_dentry = dentry;
 	d_add(dentry, inode);
-	inode_unlock(d_inode(root));
 
 	return 0;
 
 out:
-	inode_unlock(d_inode(root));
 	kfree(device);
 	iput(inode);
 
@@ -378,12 +456,9 @@ static const struct inode_operations binderfs_dir_inode_operations = {
 
 static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
 {
+	int ret;
 	struct binderfs_info *info;
-	int ret = -ENOMEM;
 	struct inode *inode = NULL;
-	struct ipc_namespace *ipc_ns = sb->s_fs_info;
-
-	get_ipc_ns(ipc_ns);
 
 	sb->s_blocksize = PAGE_SIZE;
 	sb->s_blocksize_bits = PAGE_SHIFT;
@@ -405,11 +480,17 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_op = &binderfs_super_ops;
 	sb->s_time_gran = 1;
 
-	info = kzalloc(sizeof(struct binderfs_info), GFP_KERNEL);
-	if (!info)
-		goto err_without_dentry;
+	sb->s_fs_info = kzalloc(sizeof(struct binderfs_info), GFP_KERNEL);
+	if (!sb->s_fs_info)
+		return -ENOMEM;
+	info = sb->s_fs_info;
+
+	info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
+
+	ret = binderfs_parse_mount_opts(data, &info->mount_opts);
+	if (ret)
+		return ret;
 
-	info->ipc_ns = ipc_ns;
 	info->root_gid = make_kgid(sb->s_user_ns, 0);
 	if (!gid_valid(info->root_gid))
 		info->root_gid = GLOBAL_ROOT_GID;
@@ -417,11 +498,9 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
 	if (!uid_valid(info->root_uid))
 		info->root_uid = GLOBAL_ROOT_UID;
 
-	sb->s_fs_info = info;
-
 	inode = new_inode(sb);
 	if (!inode)
-		goto err_without_dentry;
+		return -ENOMEM;
 
 	inode->i_ino = FIRST_INODE;
 	inode->i_fop = &simple_dir_operations;
@@ -432,79 +511,28 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	sb->s_root = d_make_root(inode);
 	if (!sb->s_root)
-		goto err_without_dentry;
-
-	ret = binderfs_binder_ctl_create(sb);
-	if (ret)
-		goto err_with_dentry;
-
-	return 0;
-
-err_with_dentry:
-	dput(sb->s_root);
-	sb->s_root = NULL;
-
-err_without_dentry:
-	put_ipc_ns(ipc_ns);
-	iput(inode);
-	kfree(info);
-
-	return ret;
-}
-
-static int binderfs_test_super(struct super_block *sb, void *data)
-{
-	struct binderfs_info *info = sb->s_fs_info;
-
-	if (info)
-		return info->ipc_ns == data;
-
-	return 0;
-}
+		return -ENOMEM;
 
-static int binderfs_set_super(struct super_block *sb, void *data)
-{
-	sb->s_fs_info = data;
-	return set_anon_super(sb, NULL);
+	return binderfs_binder_ctl_create(sb);
 }
 
 static struct dentry *binderfs_mount(struct file_system_type *fs_type,
 				     int flags, const char *dev_name,
 				     void *data)
 {
-	struct super_block *sb;
-	struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
-
-	if (!ns_capable(ipc_ns->user_ns, CAP_SYS_ADMIN))
-		return ERR_PTR(-EPERM);
-
-	sb = sget_userns(fs_type, binderfs_test_super, binderfs_set_super,
-			 flags, ipc_ns->user_ns, ipc_ns);
-	if (IS_ERR(sb))
-		return ERR_CAST(sb);
-
-	if (!sb->s_root) {
-		int ret = binderfs_fill_super(sb, data, flags & SB_SILENT ? 1 : 0);
-		if (ret) {
-			deactivate_locked_super(sb);
-			return ERR_PTR(ret);
-		}
-
-		sb->s_flags |= SB_ACTIVE;
-	}
-
-	return dget(sb->s_root);
+	return mount_nodev(fs_type, flags, data, binderfs_fill_super);
 }
 
 static void binderfs_kill_super(struct super_block *sb)
 {
 	struct binderfs_info *info = sb->s_fs_info;
 
+	kill_litter_super(sb);
+
 	if (info && info->ipc_ns)
 		put_ipc_ns(info->ipc_ns);
 
 	kfree(info);
-	kill_litter_super(sb);
 }
 
 static struct file_system_type binder_fs_type = {
@@ -530,14 +558,6 @@ static int __init init_binderfs(void)
 		return ret;
 	}
 
-	binderfs_mnt = kern_mount(&binder_fs_type);
-	if (IS_ERR(binderfs_mnt)) {
-		ret = PTR_ERR(binderfs_mnt);
-		binderfs_mnt = NULL;
-		unregister_filesystem(&binder_fs_type);
-		unregister_chrdev_region(binderfs_dev, BINDERFS_MAX_MINOR);
-	}
-
 	return ret;
 }