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;
 }