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![Christian Brauner](/assets/img/avatar_default.png)
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b
("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
645 lines
16 KiB
C
645 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* inode.c - part of tracefs, a pseudo file system for activating tracing
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*
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* Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
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*
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* Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
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*
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* tracefs is the file system that is used by the tracing infrastructure.
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/kobject.h>
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#include <linux/namei.h>
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#include <linux/tracefs.h>
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#include <linux/fsnotify.h>
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#include <linux/security.h>
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#include <linux/seq_file.h>
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#include <linux/parser.h>
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#include <linux/magic.h>
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#include <linux/slab.h>
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#define TRACEFS_DEFAULT_MODE 0700
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static struct vfsmount *tracefs_mount;
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static int tracefs_mount_count;
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static bool tracefs_registered;
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static ssize_t default_read_file(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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return 0;
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}
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static ssize_t default_write_file(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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return count;
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}
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static const struct file_operations tracefs_file_operations = {
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.read = default_read_file,
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.write = default_write_file,
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.open = simple_open,
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.llseek = noop_llseek,
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};
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static struct tracefs_dir_ops {
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int (*mkdir)(const char *name);
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int (*rmdir)(const char *name);
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} tracefs_ops __ro_after_init;
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static char *get_dname(struct dentry *dentry)
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{
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const char *dname;
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char *name;
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int len = dentry->d_name.len;
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dname = dentry->d_name.name;
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name = kmalloc(len + 1, GFP_KERNEL);
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if (!name)
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return NULL;
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memcpy(name, dname, len);
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name[len] = 0;
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return name;
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}
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static int tracefs_syscall_mkdir(struct mnt_idmap *idmap,
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struct inode *inode, struct dentry *dentry,
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umode_t mode)
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{
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char *name;
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int ret;
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name = get_dname(dentry);
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if (!name)
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return -ENOMEM;
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/*
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* The mkdir call can call the generic functions that create
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* the files within the tracefs system. It is up to the individual
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* mkdir routine to handle races.
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*/
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inode_unlock(inode);
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ret = tracefs_ops.mkdir(name);
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inode_lock(inode);
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kfree(name);
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return ret;
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}
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static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
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{
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char *name;
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int ret;
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name = get_dname(dentry);
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if (!name)
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return -ENOMEM;
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/*
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* The rmdir call can call the generic functions that create
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* the files within the tracefs system. It is up to the individual
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* rmdir routine to handle races.
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* This time we need to unlock not only the parent (inode) but
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* also the directory that is being deleted.
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*/
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inode_unlock(inode);
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inode_unlock(d_inode(dentry));
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ret = tracefs_ops.rmdir(name);
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inode_lock_nested(inode, I_MUTEX_PARENT);
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inode_lock(d_inode(dentry));
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kfree(name);
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return ret;
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}
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static const struct inode_operations tracefs_dir_inode_operations = {
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.lookup = simple_lookup,
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.mkdir = tracefs_syscall_mkdir,
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.rmdir = tracefs_syscall_rmdir,
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};
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static struct inode *tracefs_get_inode(struct super_block *sb)
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{
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struct inode *inode = new_inode(sb);
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if (inode) {
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inode->i_ino = get_next_ino();
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inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
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}
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return inode;
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}
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struct tracefs_mount_opts {
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kuid_t uid;
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kgid_t gid;
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umode_t mode;
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/* Opt_* bitfield. */
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unsigned int opts;
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};
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enum {
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Opt_uid,
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Opt_gid,
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Opt_mode,
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Opt_err
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};
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static const match_table_t tokens = {
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{Opt_uid, "uid=%u"},
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{Opt_gid, "gid=%u"},
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{Opt_mode, "mode=%o"},
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{Opt_err, NULL}
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};
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struct tracefs_fs_info {
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struct tracefs_mount_opts mount_opts;
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};
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static void change_gid(struct dentry *dentry, kgid_t gid)
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{
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if (!dentry->d_inode)
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return;
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dentry->d_inode->i_gid = gid;
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}
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/*
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* Taken from d_walk, but without he need for handling renames.
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* Nothing can be renamed while walking the list, as tracefs
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* does not support renames. This is only called when mounting
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* or remounting the file system, to set all the files to
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* the given gid.
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*/
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static void set_gid(struct dentry *parent, kgid_t gid)
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{
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struct dentry *this_parent;
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struct list_head *next;
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this_parent = parent;
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spin_lock(&this_parent->d_lock);
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change_gid(this_parent, gid);
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repeat:
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next = this_parent->d_subdirs.next;
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resume:
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while (next != &this_parent->d_subdirs) {
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struct list_head *tmp = next;
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struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
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next = tmp->next;
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spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
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change_gid(dentry, gid);
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if (!list_empty(&dentry->d_subdirs)) {
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spin_unlock(&this_parent->d_lock);
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spin_release(&dentry->d_lock.dep_map, _RET_IP_);
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this_parent = dentry;
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spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
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goto repeat;
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}
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spin_unlock(&dentry->d_lock);
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}
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/*
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* All done at this level ... ascend and resume the search.
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*/
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rcu_read_lock();
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ascend:
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if (this_parent != parent) {
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struct dentry *child = this_parent;
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this_parent = child->d_parent;
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spin_unlock(&child->d_lock);
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spin_lock(&this_parent->d_lock);
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/* go into the first sibling still alive */
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do {
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next = child->d_child.next;
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if (next == &this_parent->d_subdirs)
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goto ascend;
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child = list_entry(next, struct dentry, d_child);
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} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
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rcu_read_unlock();
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goto resume;
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}
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rcu_read_unlock();
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spin_unlock(&this_parent->d_lock);
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return;
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}
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static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
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{
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substring_t args[MAX_OPT_ARGS];
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int option;
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int token;
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kuid_t uid;
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kgid_t gid;
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char *p;
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opts->opts = 0;
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opts->mode = TRACEFS_DEFAULT_MODE;
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while ((p = strsep(&data, ",")) != NULL) {
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if (!*p)
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continue;
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token = match_token(p, tokens, args);
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switch (token) {
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case Opt_uid:
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if (match_int(&args[0], &option))
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return -EINVAL;
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uid = make_kuid(current_user_ns(), option);
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if (!uid_valid(uid))
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return -EINVAL;
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opts->uid = uid;
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break;
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case Opt_gid:
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if (match_int(&args[0], &option))
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return -EINVAL;
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gid = make_kgid(current_user_ns(), option);
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if (!gid_valid(gid))
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return -EINVAL;
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opts->gid = gid;
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break;
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case Opt_mode:
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if (match_octal(&args[0], &option))
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return -EINVAL;
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opts->mode = option & S_IALLUGO;
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break;
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/*
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* We might like to report bad mount options here;
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* but traditionally tracefs has ignored all mount options
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*/
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}
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opts->opts |= BIT(token);
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}
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return 0;
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}
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static int tracefs_apply_options(struct super_block *sb, bool remount)
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{
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struct tracefs_fs_info *fsi = sb->s_fs_info;
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struct inode *inode = d_inode(sb->s_root);
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struct tracefs_mount_opts *opts = &fsi->mount_opts;
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/*
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* On remount, only reset mode/uid/gid if they were provided as mount
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* options.
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*/
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if (!remount || opts->opts & BIT(Opt_mode)) {
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inode->i_mode &= ~S_IALLUGO;
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inode->i_mode |= opts->mode;
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}
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if (!remount || opts->opts & BIT(Opt_uid))
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inode->i_uid = opts->uid;
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if (!remount || opts->opts & BIT(Opt_gid)) {
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/* Set all the group ids to the mount option */
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set_gid(sb->s_root, opts->gid);
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}
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return 0;
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}
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static int tracefs_remount(struct super_block *sb, int *flags, char *data)
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{
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int err;
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struct tracefs_fs_info *fsi = sb->s_fs_info;
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sync_filesystem(sb);
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err = tracefs_parse_options(data, &fsi->mount_opts);
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if (err)
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goto fail;
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tracefs_apply_options(sb, true);
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fail:
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return err;
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}
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static int tracefs_show_options(struct seq_file *m, struct dentry *root)
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{
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struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
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struct tracefs_mount_opts *opts = &fsi->mount_opts;
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if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
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seq_printf(m, ",uid=%u",
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from_kuid_munged(&init_user_ns, opts->uid));
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if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
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seq_printf(m, ",gid=%u",
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from_kgid_munged(&init_user_ns, opts->gid));
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if (opts->mode != TRACEFS_DEFAULT_MODE)
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seq_printf(m, ",mode=%o", opts->mode);
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return 0;
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}
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static const struct super_operations tracefs_super_operations = {
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.statfs = simple_statfs,
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.remount_fs = tracefs_remount,
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.show_options = tracefs_show_options,
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};
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static int trace_fill_super(struct super_block *sb, void *data, int silent)
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{
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static const struct tree_descr trace_files[] = {{""}};
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struct tracefs_fs_info *fsi;
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int err;
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fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
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sb->s_fs_info = fsi;
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if (!fsi) {
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err = -ENOMEM;
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goto fail;
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}
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err = tracefs_parse_options(data, &fsi->mount_opts);
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if (err)
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goto fail;
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err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
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if (err)
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goto fail;
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sb->s_op = &tracefs_super_operations;
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tracefs_apply_options(sb, false);
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return 0;
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fail:
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kfree(fsi);
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sb->s_fs_info = NULL;
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return err;
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}
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static struct dentry *trace_mount(struct file_system_type *fs_type,
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int flags, const char *dev_name,
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void *data)
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{
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return mount_single(fs_type, flags, data, trace_fill_super);
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}
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static struct file_system_type trace_fs_type = {
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.owner = THIS_MODULE,
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.name = "tracefs",
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.mount = trace_mount,
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.kill_sb = kill_litter_super,
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};
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MODULE_ALIAS_FS("tracefs");
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static struct dentry *start_creating(const char *name, struct dentry *parent)
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{
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struct dentry *dentry;
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int error;
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pr_debug("tracefs: creating file '%s'\n",name);
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error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
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&tracefs_mount_count);
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if (error)
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return ERR_PTR(error);
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/* If the parent is not specified, we create it in the root.
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* We need the root dentry to do this, which is in the super
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* block. A pointer to that is in the struct vfsmount that we
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* have around.
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*/
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if (!parent)
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parent = tracefs_mount->mnt_root;
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inode_lock(d_inode(parent));
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if (unlikely(IS_DEADDIR(d_inode(parent))))
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dentry = ERR_PTR(-ENOENT);
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else
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dentry = lookup_one_len(name, parent, strlen(name));
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if (!IS_ERR(dentry) && d_inode(dentry)) {
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dput(dentry);
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dentry = ERR_PTR(-EEXIST);
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}
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if (IS_ERR(dentry)) {
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inode_unlock(d_inode(parent));
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simple_release_fs(&tracefs_mount, &tracefs_mount_count);
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}
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return dentry;
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}
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static struct dentry *failed_creating(struct dentry *dentry)
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{
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inode_unlock(d_inode(dentry->d_parent));
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dput(dentry);
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simple_release_fs(&tracefs_mount, &tracefs_mount_count);
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return NULL;
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}
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static struct dentry *end_creating(struct dentry *dentry)
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{
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inode_unlock(d_inode(dentry->d_parent));
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return dentry;
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}
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/**
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* tracefs_create_file - create a file in the tracefs filesystem
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* @name: a pointer to a string containing the name of the file to create.
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* @mode: the permission that the file should have.
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* @parent: a pointer to the parent dentry for this file. This should be a
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* directory dentry if set. If this parameter is NULL, then the
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* file will be created in the root of the tracefs filesystem.
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* @data: a pointer to something that the caller will want to get to later
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* on. The inode.i_private pointer will point to this value on
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* the open() call.
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* @fops: a pointer to a struct file_operations that should be used for
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* this file.
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*
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* This is the basic "create a file" function for tracefs. It allows for a
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* wide range of flexibility in creating a file, or a directory (if you want
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* to create a directory, the tracefs_create_dir() function is
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* recommended to be used instead.)
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*
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* This function will return a pointer to a dentry if it succeeds. This
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* pointer must be passed to the tracefs_remove() function when the file is
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* to be removed (no automatic cleanup happens if your module is unloaded,
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* you are responsible here.) If an error occurs, %NULL will be returned.
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*
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* If tracefs is not enabled in the kernel, the value -%ENODEV will be
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* returned.
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*/
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struct dentry *tracefs_create_file(const char *name, umode_t mode,
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struct dentry *parent, void *data,
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const struct file_operations *fops)
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{
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struct dentry *dentry;
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struct inode *inode;
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if (security_locked_down(LOCKDOWN_TRACEFS))
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return NULL;
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if (!(mode & S_IFMT))
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mode |= S_IFREG;
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BUG_ON(!S_ISREG(mode));
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dentry = start_creating(name, parent);
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if (IS_ERR(dentry))
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return NULL;
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inode = tracefs_get_inode(dentry->d_sb);
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if (unlikely(!inode))
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return failed_creating(dentry);
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inode->i_mode = mode;
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inode->i_fop = fops ? fops : &tracefs_file_operations;
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inode->i_private = data;
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inode->i_uid = d_inode(dentry->d_parent)->i_uid;
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inode->i_gid = d_inode(dentry->d_parent)->i_gid;
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d_instantiate(dentry, inode);
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fsnotify_create(d_inode(dentry->d_parent), dentry);
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return end_creating(dentry);
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}
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static struct dentry *__create_dir(const char *name, struct dentry *parent,
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const struct inode_operations *ops)
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{
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struct dentry *dentry = start_creating(name, parent);
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struct inode *inode;
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|
|
|
if (IS_ERR(dentry))
|
|
return NULL;
|
|
|
|
inode = tracefs_get_inode(dentry->d_sb);
|
|
if (unlikely(!inode))
|
|
return failed_creating(dentry);
|
|
|
|
/* Do not set bits for OTH */
|
|
inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
|
|
inode->i_op = ops;
|
|
inode->i_fop = &simple_dir_operations;
|
|
inode->i_uid = d_inode(dentry->d_parent)->i_uid;
|
|
inode->i_gid = d_inode(dentry->d_parent)->i_gid;
|
|
|
|
/* directory inodes start off with i_nlink == 2 (for "." entry) */
|
|
inc_nlink(inode);
|
|
d_instantiate(dentry, inode);
|
|
inc_nlink(d_inode(dentry->d_parent));
|
|
fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
|
|
return end_creating(dentry);
|
|
}
|
|
|
|
/**
|
|
* tracefs_create_dir - create a directory in the tracefs filesystem
|
|
* @name: a pointer to a string containing the name of the directory to
|
|
* create.
|
|
* @parent: a pointer to the parent dentry for this file. This should be a
|
|
* directory dentry if set. If this parameter is NULL, then the
|
|
* directory will be created in the root of the tracefs filesystem.
|
|
*
|
|
* This function creates a directory in tracefs with the given name.
|
|
*
|
|
* This function will return a pointer to a dentry if it succeeds. This
|
|
* pointer must be passed to the tracefs_remove() function when the file is
|
|
* to be removed. If an error occurs, %NULL will be returned.
|
|
*
|
|
* If tracing is not enabled in the kernel, the value -%ENODEV will be
|
|
* returned.
|
|
*/
|
|
struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
|
|
{
|
|
return __create_dir(name, parent, &simple_dir_inode_operations);
|
|
}
|
|
|
|
/**
|
|
* tracefs_create_instance_dir - create the tracing instances directory
|
|
* @name: The name of the instances directory to create
|
|
* @parent: The parent directory that the instances directory will exist
|
|
* @mkdir: The function to call when a mkdir is performed.
|
|
* @rmdir: The function to call when a rmdir is performed.
|
|
*
|
|
* Only one instances directory is allowed.
|
|
*
|
|
* The instances directory is special as it allows for mkdir and rmdir
|
|
* to be done by userspace. When a mkdir or rmdir is performed, the inode
|
|
* locks are released and the methods passed in (@mkdir and @rmdir) are
|
|
* called without locks and with the name of the directory being created
|
|
* within the instances directory.
|
|
*
|
|
* Returns the dentry of the instances directory.
|
|
*/
|
|
__init struct dentry *tracefs_create_instance_dir(const char *name,
|
|
struct dentry *parent,
|
|
int (*mkdir)(const char *name),
|
|
int (*rmdir)(const char *name))
|
|
{
|
|
struct dentry *dentry;
|
|
|
|
/* Only allow one instance of the instances directory. */
|
|
if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
|
|
return NULL;
|
|
|
|
dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
|
|
if (!dentry)
|
|
return NULL;
|
|
|
|
tracefs_ops.mkdir = mkdir;
|
|
tracefs_ops.rmdir = rmdir;
|
|
|
|
return dentry;
|
|
}
|
|
|
|
static void remove_one(struct dentry *victim)
|
|
{
|
|
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
|
|
}
|
|
|
|
/**
|
|
* tracefs_remove - recursively removes a directory
|
|
* @dentry: a pointer to a the dentry of the directory to be removed.
|
|
*
|
|
* This function recursively removes a directory tree in tracefs that
|
|
* was previously created with a call to another tracefs function
|
|
* (like tracefs_create_file() or variants thereof.)
|
|
*/
|
|
void tracefs_remove(struct dentry *dentry)
|
|
{
|
|
if (IS_ERR_OR_NULL(dentry))
|
|
return;
|
|
|
|
simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
|
|
simple_recursive_removal(dentry, remove_one);
|
|
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
|
|
}
|
|
|
|
/**
|
|
* tracefs_initialized - Tells whether tracefs has been registered
|
|
*/
|
|
bool tracefs_initialized(void)
|
|
{
|
|
return tracefs_registered;
|
|
}
|
|
|
|
static int __init tracefs_init(void)
|
|
{
|
|
int retval;
|
|
|
|
retval = sysfs_create_mount_point(kernel_kobj, "tracing");
|
|
if (retval)
|
|
return -EINVAL;
|
|
|
|
retval = register_filesystem(&trace_fs_type);
|
|
if (!retval)
|
|
tracefs_registered = true;
|
|
|
|
return retval;
|
|
}
|
|
core_initcall(tracefs_init);
|