diff options
| -rw-r--r-- | Documentation/filesystems/debugfs.txt | 5 | ||||
| -rw-r--r-- | fs/debugfs/inode.c | 149 |
2 files changed, 152 insertions, 2 deletions
diff --git a/Documentation/filesystems/debugfs.txt b/Documentation/filesystems/debugfs.txt index 6872c91bce3..4e257587318 100644 --- a/Documentation/filesystems/debugfs.txt +++ b/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. diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index 956d5ddddf6..b80bc846a15 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, |