proc: Add fs_context support to procfs

Add fs_context support to procfs.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 129 insertions, 68 deletions

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 17b5261206dd..fc7e38def174 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -127,7 +127,6 @@ const struct super_operations proc_sops = {
         .drop_inode     = generic_delete_inode,
         .evict_inode    = proc_evict_inode,
         .statfs         = simple_statfs,
-        .remount_fs     = proc_remount,
         .show_options   = proc_show_options,
 };
 
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 97157c0410a2..40f905143d39 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -270,7 +270,6 @@ static inline void proc_tty_init(void) {}
 extern struct proc_dir_entry proc_root;
 
 extern void proc_self_init(void);
-extern int proc_remount(struct super_block *, int *, char *);
 
 /*
  * task_[no]mmu.c
diff --git a/fs/proc/root.c b/fs/proc/root.c
index fe4f64b3250b..6927b29ece76 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -19,74 +19,89 @@
 #include <linux/module.h>
 #include <linux/bitops.h>
 #include <linux/user_namespace.h>
+#include <linux/fs_context.h>
 #include <linux/mount.h>
 #include <linux/pid_namespace.h>
-#include <linux/parser.h>
+#include <linux/fs_parser.h>
 #include <linux/cred.h>
 #include <linux/magic.h>
+#include <linux/slab.h>
 
 #include "internal.h"
 
-enum {
-        Opt_gid, Opt_hidepid, Opt_err,
+struct proc_fs_context {
+        struct pid_namespace    *pid_ns;
+        unsigned int            mask;
+        int                     hidepid;
+        int                     gid;
 };
 
-static const match_table_t tokens = {
-        {Opt_hidepid, "hidepid=%u"},
-        {Opt_gid, "gid=%u"},
-        {Opt_err, NULL},
+enum proc_param {
+        Opt_gid,
+        Opt_hidepid,
 };
 
-static int proc_parse_options(char *options, struct pid_namespace *pid)
+static const struct fs_parameter_spec proc_param_specs[] = {
+        fsparam_u32("gid",      Opt_gid),
+        fsparam_u32("hidepid",  Opt_hidepid),
+        {}
+};
+
+static const struct fs_parameter_description proc_fs_parameters = {
+        .name           = "proc",
+        .specs          = proc_param_specs,
+};
+
+static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
-        char *p;
-        substring_t args[MAX_OPT_ARGS];
-        int option;
-
-        if (!options)
-                return 1;
-
-        while ((p = strsep(&options, ",")) != NULL) {
-                int token;
-                if (!*p)
-                        continue;
-
-                args[0].to = args[0].from = NULL;
-                token = match_token(p, tokens, args);
-                switch (token) {
-                case Opt_gid:
-                        if (match_int(&args[0], &option))
-                                return 0;
-                        pid->pid_gid = make_kgid(current_user_ns(), option);
-                        break;
-                case Opt_hidepid:
-                        if (match_int(&args[0], &option))
-                                return 0;
-                        if (option < HIDEPID_OFF ||
-                            option > HIDEPID_INVISIBLE) {
-                                pr_err("proc: hidepid value must be between 0 and 2.\n");
-                                return 0;
-                        }
-                        pid->hide_pid = option;
-                        break;
-                default:
-                        pr_err("proc: unrecognized mount option \"%s\" "
-                               "or missing value\n", p);
-                        return 0;
-                }
+        struct proc_fs_context *ctx = fc->fs_private;
+        struct fs_parse_result result;
+        int opt;
+
+        opt = fs_parse(fc, &proc_fs_parameters, param, &result);
+        if (opt < 0)
+                return opt;
+
+        switch (opt) {
+        case Opt_gid:
+                ctx->gid = result.uint_32;
+                break;
+
+        case Opt_hidepid:
+                ctx->hidepid = result.uint_32;
+                if (ctx->hidepid < HIDEPID_OFF ||
+                    ctx->hidepid > HIDEPID_INVISIBLE)
+                        return invalf(fc, "proc: hidepid value must be between 0 and 2.\n");
+                break;
+
+        default:
+                return -EINVAL;
         }
 
-        return 1;
+        ctx->mask |= 1 << opt;
+        return 0;
+}
+
+static void proc_apply_options(struct super_block *s,
+                               struct fs_context *fc,
+                               struct pid_namespace *pid_ns,
+                               struct user_namespace *user_ns)
+{
+        struct proc_fs_context *ctx = fc->fs_private;
+
+        if (ctx->mask & (1 << Opt_gid))
+                pid_ns->pid_gid = make_kgid(user_ns, ctx->gid);
+        if (ctx->mask & (1 << Opt_hidepid))
+                pid_ns->hide_pid = ctx->hidepid;
 }
 
-static int proc_fill_super(struct super_block *s, void *data, int silent)
+static int proc_fill_super(struct super_block *s, struct fs_context *fc)
 {
-        struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
+        struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info);
         struct inode *root_inode;
         int ret;
 
-        if (!proc_parse_options(data, ns))
-                return -EINVAL;
+        proc_apply_options(s, fc, pid_ns, current_user_ns());
 
         /* User space would break if executables or devices appear on proc */
         s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
@@ -127,27 +142,55 @@ static int proc_fill_super(struct super_block *s, void *data, int silent)
         return proc_setup_thread_self(s);
 }
 
-int proc_remount(struct super_block *sb, int *flags, char *data)
+static int proc_reconfigure(struct fs_context *fc)
 {
+        struct super_block *sb = fc->root->d_sb;
         struct pid_namespace *pid = sb->s_fs_info;
 
         sync_filesystem(sb);
-        return !proc_parse_options(data, pid);
+
+        proc_apply_options(sb, fc, pid, current_user_ns());
+        return 0;
 }
 
-static struct dentry *proc_mount(struct file_system_type *fs_type,
-        int flags, const char *dev_name, void *data)
+static int proc_get_tree(struct fs_context *fc)
 {
-        struct pid_namespace *ns;
+        struct proc_fs_context *ctx = fc->fs_private;
 
-        if (flags & SB_KERNMOUNT) {
-                ns = data;
-                data = NULL;
-        } else {
-                ns = task_active_pid_ns(current);
-        }
+        put_user_ns(fc->user_ns);
+        fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
+        fc->s_fs_info = ctx->pid_ns;
+        return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super);
+}
+
+static void proc_fs_context_free(struct fs_context *fc)
+{
+        struct proc_fs_context *ctx = fc->fs_private;
+
+        if (ctx->pid_ns)
+                put_pid_ns(ctx->pid_ns);
+        kfree(ctx);
+}
+
+static const struct fs_context_operations proc_fs_context_ops = {
+        .free           = proc_fs_context_free,
+        .parse_param    = proc_parse_param,
+        .get_tree       = proc_get_tree,
+        .reconfigure    = proc_reconfigure,
+};
+
+static int proc_init_fs_context(struct fs_context *fc)
+{
+        struct proc_fs_context *ctx;
+
+        ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
+        if (!ctx)
+                return -ENOMEM;
 
-        return mount_ns(fs_type, flags, data, ns, ns->user_ns, proc_fill_super);
+        ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
+        fc->fs_private = ctx;
+        fc->ops = &proc_fs_context_ops;
+        return 0;
 }
 
 static void proc_kill_sb(struct super_block *sb)
@@ -164,10 +207,11 @@ static void proc_kill_sb(struct super_block *sb)
 }
 
 static struct file_system_type proc_fs_type = {
-        .name           = "proc",
-        .mount          = proc_mount,
-        .kill_sb        = proc_kill_sb,
-        .fs_flags       = FS_USERNS_MOUNT,
+        .name                   = "proc",
+        .init_fs_context        = proc_init_fs_context,
+        .parameters             = &proc_fs_parameters,
+        .kill_sb                = proc_kill_sb,
+        .fs_flags               = FS_USERNS_MOUNT,
 };
 
 void __init proc_root_init(void)
@@ -205,7 +249,7 @@ static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentr
 {
         if (!proc_pid_lookup(dir, dentry, flags))
                 return NULL;
-        
+
         return proc_lookup(dir, dentry, flags);
 }
 
@@ -258,9 +302,28 @@ struct proc_dir_entry proc_root = {
 
 int pid_ns_prepare_proc(struct pid_namespace *ns)
 {
+        struct proc_fs_context *ctx;
+        struct fs_context *fc;
         struct vfsmount *mnt;
 
-        mnt = kern_mount_data(&proc_fs_type, ns);
+        fc = fs_context_for_mount(&proc_fs_type, SB_KERNMOUNT);
+        if (IS_ERR(fc))
+                return PTR_ERR(fc);
+
+        if (fc->user_ns != ns->user_ns) {
+                put_user_ns(fc->user_ns);
+                fc->user_ns = get_user_ns(ns->user_ns);
+        }
+
+        ctx = fc->fs_private;
+        if (ctx->pid_ns != ns) {
+                put_pid_ns(ctx->pid_ns);
+                get_pid_ns(ns);
+                ctx->pid_ns = ns;
+        }
+
+        mnt = fc_mount(fc);
+        put_fs_context(fc);
         if (IS_ERR(mnt))
                 return PTR_ERR(mnt);