---

yaml
---
r: 288846
b: refs/heads/master
c: d6e4868
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 9875bb480cc89d9b690f7028aadf7e58454f0dae
+refs/heads/master: d6e486868cde585842d55ba3b6ec57af090fc343

trunk/Documentation/filesystems/debugfs.txt

@@ -14,7 +14,10 @@ Debugfs is typically mounted with a command like:
 
     mount -t debugfs none /sys/kernel/debug
 
-(Or an equivalent /etc/fstab line). 
+(Or an equivalent /etc/fstab line).
+The debugfs root directory is accessible by anyone by default. To
+restrict access to the tree the "uid", "gid" and "mode" mount
+options can be used.
 
 Note that the debugfs API is exported GPL-only to modules.
 

trunk/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,