1 files changed, 49 insertions, 5 deletions

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 4e42aba97f2e..ef6840c64e95 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -26,6 +26,21 @@
 
 #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,
 };
@@ -36,7 +51,7 @@ static const match_table_t tokens = {
 	{Opt_err, NULL},
 };
 
-int proc_parse_options(char *options, struct pid_namespace *pid)
+static int proc_parse_options(char *options, struct pid_namespace *pid)
 {
 	char *p;
 	substring_t args[MAX_OPT_ARGS];
@@ -89,16 +104,45 @@ 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 = data;
-		data = NULL;
+		ns = (struct pid_namespace *)data;
+		options = 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);
 	}
 
-	return mount_ns(fs_type, flags, data, ns, ns->user_ns, proc_fill_super);
+	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);
 }
 
 static void proc_kill_sb(struct super_block *sb)
@@ -136,7 +180,7 @@ void __init proc_root_init(void)
 	proc_symlink("mounts", NULL, "self/mounts");
 
 	proc_net_init();
-
+	proc_uid_init();
 #ifdef CONFIG_SYSVIPC
 	proc_mkdir("sysvipc", NULL);
 #endif