1 files changed, 148 insertions, 1 deletions

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 956d5ddddf6e..b80bc846a15a 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -23,9 +23,13 @@
 #include <linux/debugfs.h>
 #include <linux/fsnotify.h>
 #include <linux/string.h>
+#include <linux/seq_file.h>
+#include <linux/parser.h>
 #include <linux/magic.h>
 #include <linux/slab.h>
 
+#define DEBUGFS_DEFAULT_MODE    0755
+
 static struct vfsmount *debugfs_mount;
 static int debugfs_mount_count;
 static bool debugfs_registered;
@@ -125,11 +129,154 @@ static inline int debugfs_positive(struct dentry *dentry)
         return dentry->d_inode && !d_unhashed(dentry);
 }
 
+struct debugfs_mount_opts {
+        uid_t uid;
+        gid_t gid;
+        umode_t mode;
+};
+
+enum {
+        Opt_uid,
+        Opt_gid,
+        Opt_mode,
+        Opt_err
+};
+
+static const match_table_t tokens = {
+        {Opt_uid, "uid=%u"},
+        {Opt_gid, "gid=%u"},
+        {Opt_mode, "mode=%o"},
+        {Opt_err, NULL}
+};
+
+struct debugfs_fs_info {
+        struct debugfs_mount_opts mount_opts;
+};
+
+static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
+{
+        substring_t args[MAX_OPT_ARGS];
+        int option;
+        int token;
+        char *p;
+
+        opts->mode = DEBUGFS_DEFAULT_MODE;
+
+        while ((p = strsep(&data, ",")) != NULL) {
+                if (!*p)
+                        continue;
+
+                token = match_token(p, tokens, args);
+                switch (token) {
+                case Opt_uid:
+                        if (match_int(&args[0], &option))
+                                return -EINVAL;
+                        opts->uid = option;
+                        break;
+                case Opt_gid:
+                        if (match_octal(&args[0], &option))
+                                return -EINVAL;
+                        opts->gid = option;
+                        break;
+                case Opt_mode:
+                        if (match_octal(&args[0], &option))
+                                return -EINVAL;
+                        opts->mode = option & S_IALLUGO;
+                        break;
+                /*
+                 * We might like to report bad mount options here;
+                 * but traditionally debugfs has ignored all mount options
+                 */
+                }
+        }
+
+        return 0;
+}
+
+static int debugfs_apply_options(struct super_block *sb)
+{
+        struct debugfs_fs_info *fsi = sb->s_fs_info;
+        struct inode *inode = sb->s_root->d_inode;
+        struct debugfs_mount_opts *opts = &fsi->mount_opts;
+
+        inode->i_mode &= ~S_IALLUGO;
+        inode->i_mode |= opts->mode;
+
+        inode->i_uid = opts->uid;
+        inode->i_gid = opts->gid;
+
+        return 0;
+}
+
+static int debugfs_remount(struct super_block *sb, int *flags, char *data)
+{
+        int err;
+        struct debugfs_fs_info *fsi = sb->s_fs_info;
+
+        err = debugfs_parse_options(data, &fsi->mount_opts);
+        if (err)
+                goto fail;
+
+        debugfs_apply_options(sb);
+
+fail:
+        return err;
+}
+
+static int debugfs_show_options(struct seq_file *m, struct dentry *root)
+{
+        struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
+        struct debugfs_mount_opts *opts = &fsi->mount_opts;
+
+        if (opts->uid != 0)
+                seq_printf(m, ",uid=%u", opts->uid);
+        if (opts->gid != 0)
+                seq_printf(m, ",gid=%u", opts->gid);
+        if (opts->mode != DEBUGFS_DEFAULT_MODE)
+                seq_printf(m, ",mode=%o", opts->mode);
+
+        return 0;
+}
+
+static const struct super_operations debugfs_super_operations = {
+        .statfs         = simple_statfs,
+        .remount_fs     = debugfs_remount,
+        .show_options   = debugfs_show_options,
+};
+
 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 {
         static struct tree_descr debug_files[] = {{""}};
+        struct debugfs_fs_info *fsi;
+        int err;
+
+        save_mount_options(sb, data);
+
+        fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
+        sb->s_fs_info = fsi;
+        if (!fsi) {
+                err = -ENOMEM;
+                goto fail;
+        }
+
+        err = debugfs_parse_options(data, &fsi->mount_opts);
+        if (err)
+                goto fail;
+
+        err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
+        if (err)
+                goto fail;
+
+        sb->s_op = &debugfs_super_operations;
+
+        debugfs_apply_options(sb);
+
+        return 0;
 
-        return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
+fail:
+        kfree(fsi);
+        sb->s_fs_info = NULL;
+        return err;
 }
 
 static struct dentry *debug_mount(struct file_system_type *fs_type,