proc: Convert proc_mount to use mount_ns.

Move the call of get_pid_ns, the call of proc_parse_options, and
the setting of s_iflags into proc_fill_super so that mount_ns
can be used.

Convert proc_mount to call mount_ns and remove the now unnecessary
code.

Acked-by: Seth Forshee <seth.forshee@canonical.com>
Reviewed-by: Djalal Harouni <tixxdz@gmail.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

3 files changed, 13 insertions, 51 deletions

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 78fa452d65ed..f4817efb25a6 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -457,12 +457,17 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
         return inode;
 }
 
-int proc_fill_super(struct super_block *s)
+int proc_fill_super(struct super_block *s, void *data, int silent)
 {
+        struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
         struct inode *root_inode;
         int ret;
 
-        s->s_iflags |= SB_I_USERNS_VISIBLE;
+        if (!proc_parse_options(data, ns))
+                return -EINVAL;
+
+        /* User space would break if executables appear on proc */
+        s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC;
         s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
         s->s_blocksize = 1024;
         s->s_blocksize_bits = 10;
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index aa2781095bd1..7931c558c192 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -212,7 +212,7 @@ extern const struct inode_operations proc_pid_link_inode_operations;
 
 extern void proc_init_inodecache(void);
 extern struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
-extern int proc_fill_super(struct super_block *);
+extern int proc_fill_super(struct super_block *, void *data, int flags);
 extern void proc_entry_rundown(struct proc_dir_entry *);
 
 /*
@@ -268,6 +268,7 @@ static inline void proc_tty_init(void) {}
  * root.c
  */
 extern struct proc_dir_entry proc_root;
+extern int proc_parse_options(char *options, struct pid_namespace *pid);
 
 extern void proc_self_init(void);
 extern int proc_remount(struct super_block *, int *, char *);
diff --git a/fs/proc/root.c b/fs/proc/root.c
index a1b2860fec62..8d3e484055a6 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -23,21 +23,6 @@
 
 #include "internal.h"
 
-static int proc_test_super(struct super_block *sb, void *data)
-{
-        return sb->s_fs_info == data;
-}
-
-static int proc_set_super(struct super_block *sb, void *data)
-{
-        int err = set_anon_super(sb, NULL);
-        if (!err) {
-                struct pid_namespace *ns = (struct pid_namespace *)data;
-                sb->s_fs_info = get_pid_ns(ns);
-        }
-        return err;
-}
-
 enum {
         Opt_gid, Opt_hidepid, Opt_err,
 };
@@ -48,7 +33,7 @@ static const match_table_t tokens = {
         {Opt_err, NULL},
 };
 
-static int proc_parse_options(char *options, struct pid_namespace *pid)
+int proc_parse_options(char *options, struct pid_namespace *pid)
 {
         char *p;
         substring_t args[MAX_OPT_ARGS];
@@ -100,45 +85,16 @@ int proc_remount(struct super_block *sb, int *flags, char *data)
 static struct dentry *proc_mount(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *data)
 {
-        int err;
-        struct super_block *sb;
         struct pid_namespace *ns;
-        char *options;
 
         if (flags & MS_KERNMOUNT) {
-                ns = (struct pid_namespace *)data;
-                options = NULL;
+                ns = data;
+                data = NULL;
         } else {
                 ns = task_active_pid_ns(current);
-                options = data;
-
-                /* Does the mounter have privilege over the pid namespace? */
-                if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
-                        return ERR_PTR(-EPERM);
-        }
-
-        sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
-        if (IS_ERR(sb))
-                return ERR_CAST(sb);
-
-        if (!proc_parse_options(options, ns)) {
-                deactivate_locked_super(sb);
-                return ERR_PTR(-EINVAL);
-        }
-
-        if (!sb->s_root) {
-                err = proc_fill_super(sb);
-                if (err) {
-                        deactivate_locked_super(sb);
-                        return ERR_PTR(err);
-                }
-
-                sb->s_flags |= MS_ACTIVE;
-                /* User space would break if executables appear on proc */
-                sb->s_iflags |= SB_I_NOEXEC;
         }
 
-        return dget(sb->s_root);
+        return mount_ns(fs_type, flags, data, ns, ns->user_ns, proc_fill_super);
 }
 
 static void proc_kill_sb(struct super_block *sb)