procfs: parse mount options

Add support for procfs mount options.  Actual mount options are coming in
the next patches.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Greg KH <greg@kroah.com>
Cc: Theodore Tso <tytso@MIT.EDU>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: James Morris <jmorris@namei.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 64 insertions, 2 deletions

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 51a176622b8f..27c762f34870 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -7,6 +7,7 @@
 #include <linux/time.h>
 #include <linux/proc_fs.h>
 #include <linux/kernel.h>
+#include <linux/pid_namespace.h>
 #include <linux/mm.h>
 #include <linux/string.h>
 #include <linux/stat.h>
@@ -17,7 +18,9 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/sysctl.h>
+#include <linux/seq_file.h>
 #include <linux/slab.h>
+#include <linux/mount.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -101,12 +104,19 @@ void __init proc_init_inodecache(void)
                                              init_once);
 }
 
+static int proc_show_options(struct seq_file *seq, struct dentry *root)
+{
+        return 0;
+}
+
 static const struct super_operations proc_sops = {
         .alloc_inode    = proc_alloc_inode,
         .destroy_inode  = proc_destroy_inode,
         .drop_inode     = generic_delete_inode,
         .evict_inode    = proc_evict_inode,
         .statfs         = simple_statfs,
+        .remount_fs     = proc_remount,
+        .show_options   = proc_show_options,
 };
 
 static void __pde_users_dec(struct proc_dir_entry *pde)
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 7838e5cfec14..292577531ad1 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -117,6 +117,7 @@ void pde_put(struct proc_dir_entry *pde);
 
 int proc_fill_super(struct super_block *);
 struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
+int proc_remount(struct super_block *sb, int *flags, char *data);
 
 /*
  * These are generic /proc routines that use the internal
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 03102d978180..6a8ac1d361a9 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -18,6 +18,7 @@
 #include <linux/bitops.h>
 #include <linux/mount.h>
 #include <linux/pid_namespace.h>
+#include <linux/parser.h>
 
 #include "internal.h"
 
@@ -36,6 +37,48 @@ static int proc_set_super(struct super_block *sb, void *data)
         return err;
 }
 
+enum {
+        Opt_err,
+};
+
+static const match_table_t tokens = {
+        {Opt_err, NULL},
+};
+
+static int proc_parse_options(char *options, struct pid_namespace *pid)
+{
+        char *p;
+        substring_t args[MAX_OPT_ARGS];
+
+        pr_debug("proc: options = %s\n", options);
+
+        if (!options)
+                return 1;
+
+        while ((p = strsep(&options, ",")) != NULL) {
+                int token;
+                if (!*p)
+                        continue;
+
+                args[0].to = args[0].from = 0;
+                token = match_token(p, tokens, args);
+                switch (token) {
+                default:
+                        pr_err("proc: unrecognized mount option \"%s\" "
+                               "or missing value\n", p);
+                        return 0;
+                }
+        }
+
+        return 1;
+}
+
+int proc_remount(struct super_block *sb, int *flags, char *data)
+{
+        struct pid_namespace *pid = sb->s_fs_info;
+        return !proc_parse_options(data, pid);
+}
+
 static struct dentry *proc_mount(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *data)
 {
@@ -43,11 +86,15 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
         struct super_block *sb;
         struct pid_namespace *ns;
         struct proc_inode *ei;
+        char *options;
 
-        if (flags & MS_KERNMOUNT)
+        if (flags & MS_KERNMOUNT) {
                 ns = (struct pid_namespace *)data;
-        else
+                options = NULL;
+        } else {
                 ns = current->nsproxy->pid_ns;
+                options = data;
+        }
 
         sb = sget(fs_type, proc_test_super, proc_set_super, ns);
         if (IS_ERR(sb))
@@ -55,6 +102,10 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
 
         if (!sb->s_root) {
                 sb->s_flags = flags;
+                if (!proc_parse_options(options, ns)) {
+                        deactivate_locked_super(sb);
+                        return ERR_PTR(-EINVAL);
+                }
                 err = proc_fill_super(sb);
                 if (err) {
                         deactivate_locked_super(sb);