mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-27 03:10:12 +00:00
![Linus Torvalds](/assets/img/avatar_default.png)
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Merge tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping
Pull vfs idmapping updates from Christian Brauner:
- Last cycle we introduced the dedicated struct mnt_idmap type for
mount idmapping and the required infrastucture in 256c8aed2b
("fs:
introduce dedicated idmap type for mounts"). As promised in last
cycle's pull request message this converts everything to rely on
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 relevant on the mount level. Especially for
non-vfs developers without detailed knowledge in this area this was a
potential source for bugs.
This finishes the conversion. Instead of passing the plain namespace
around this updates all places that currently take a pointer to a
mnt_userns with a pointer to struct mnt_idmap.
Now that the conversion is done all helpers down to the really
low-level helpers only accept a struct mnt_idmap argument instead of
two namespace arguments.
Conflating mount and other idmappings will now cause the compiler to
complain loudly thus eliminating the possibility of any bugs. This
makes it impossible for filesystem developers to mix up mount and
filesystem idmappings as they are two distinct types and require
distinct helpers that cannot be used interchangeably.
Everything associated with struct mnt_idmap is moved into a single
separate file. With that change no code can poke around in struct
mnt_idmap. It can only be interacted with through dedicated helpers.
That means all filesystems are and all of the vfs is completely
oblivious to the actual implementation of idmappings.
We are now also able to extend struct mnt_idmap as we see fit. For
example, we can decouple it completely from namespaces for users that
don't require or don't want to use them at all. We can also extend
the concept of idmappings so we can cover filesystem specific
requirements.
In combination with the vfs{g,u}id_t work we finished in v6.2 this
makes this feature substantially more robust and thus difficult to
implement wrong by a given filesystem and also protects the vfs.
- Enable idmapped mounts for tmpfs and fulfill a longstanding request.
A long-standing request from users had been to make it possible to
create idmapped mounts for tmpfs. For example, to share the host's
tmpfs mount between multiple sandboxes. This is a prerequisite for
some advanced Kubernetes cases. Systemd also has a range of use-cases
to increase service isolation. And there are more users of this.
However, with all of the other work going on this was way down on the
priority list but luckily someone other than ourselves picked this
up.
As usual the patch is tiny as all the infrastructure work had been
done multiple kernel releases ago. In addition to all the tests that
we already have I requested that Rodrigo add a dedicated tmpfs
testsuite for idmapped mounts to xfstests. It is to be included into
xfstests during the v6.3 development cycle. This should add a slew of
additional tests.
* tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: (26 commits)
shmem: support idmapped mounts for tmpfs
fs: move mnt_idmap
fs: port vfs{g,u}id helpers to mnt_idmap
fs: port fs{g,u}id helpers to mnt_idmap
fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap
fs: port i_{g,u}id_{needs_}update() to mnt_idmap
quota: port to mnt_idmap
fs: port privilege checking helpers to mnt_idmap
fs: port inode_owner_or_capable() to mnt_idmap
fs: port inode_init_owner() to mnt_idmap
fs: port acl to mnt_idmap
fs: port xattr to mnt_idmap
fs: port ->permission() to pass mnt_idmap
fs: port ->fileattr_set() to pass mnt_idmap
fs: port ->set_acl() to pass mnt_idmap
fs: port ->get_acl() to pass mnt_idmap
fs: port ->tmpfile() to pass mnt_idmap
fs: port ->rename() to pass mnt_idmap
fs: port ->mknod() to pass mnt_idmap
fs: port ->mkdir() to pass mnt_idmap
...
427 lines
8.9 KiB
C
427 lines
8.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/sched/signal.h>
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#include <linux/errno.h>
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#include <linux/dcache.h>
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#include <linux/path.h>
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#include <linux/fdtable.h>
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#include <linux/namei.h>
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#include <linux/pid.h>
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#include <linux/ptrace.h>
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#include <linux/bitmap.h>
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#include <linux/security.h>
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#include <linux/file.h>
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#include <linux/seq_file.h>
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#include <linux/fs.h>
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#include <linux/filelock.h>
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#include <linux/proc_fs.h>
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#include "../mount.h"
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#include "internal.h"
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#include "fd.h"
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static int seq_show(struct seq_file *m, void *v)
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{
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struct files_struct *files = NULL;
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int f_flags = 0, ret = -ENOENT;
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struct file *file = NULL;
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struct task_struct *task;
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task = get_proc_task(m->private);
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if (!task)
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return -ENOENT;
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task_lock(task);
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files = task->files;
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if (files) {
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unsigned int fd = proc_fd(m->private);
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spin_lock(&files->file_lock);
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file = files_lookup_fd_locked(files, fd);
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if (file) {
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struct fdtable *fdt = files_fdtable(files);
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f_flags = file->f_flags;
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if (close_on_exec(fd, fdt))
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f_flags |= O_CLOEXEC;
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get_file(file);
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ret = 0;
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}
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spin_unlock(&files->file_lock);
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}
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task_unlock(task);
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put_task_struct(task);
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if (ret)
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return ret;
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seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\nino:\t%lu\n",
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(long long)file->f_pos, f_flags,
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real_mount(file->f_path.mnt)->mnt_id,
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file_inode(file)->i_ino);
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/* show_fd_locks() never deferences files so a stale value is safe */
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show_fd_locks(m, file, files);
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if (seq_has_overflowed(m))
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goto out;
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if (file->f_op->show_fdinfo)
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file->f_op->show_fdinfo(m, file);
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out:
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fput(file);
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return 0;
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}
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static int proc_fdinfo_access_allowed(struct inode *inode)
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{
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bool allowed = false;
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struct task_struct *task = get_proc_task(inode);
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if (!task)
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return -ESRCH;
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allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
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put_task_struct(task);
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if (!allowed)
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return -EACCES;
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return 0;
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}
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static int seq_fdinfo_open(struct inode *inode, struct file *file)
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{
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int ret = proc_fdinfo_access_allowed(inode);
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if (ret)
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return ret;
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return single_open(file, seq_show, inode);
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}
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static const struct file_operations proc_fdinfo_file_operations = {
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.open = seq_fdinfo_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
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{
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struct file *file;
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rcu_read_lock();
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file = task_lookup_fd_rcu(task, fd);
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if (file)
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*mode = file->f_mode;
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rcu_read_unlock();
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return !!file;
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}
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static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
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fmode_t f_mode)
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{
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task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
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if (S_ISLNK(inode->i_mode)) {
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unsigned i_mode = S_IFLNK;
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if (f_mode & FMODE_READ)
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i_mode |= S_IRUSR | S_IXUSR;
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if (f_mode & FMODE_WRITE)
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i_mode |= S_IWUSR | S_IXUSR;
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inode->i_mode = i_mode;
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}
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security_task_to_inode(task, inode);
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}
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static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
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{
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struct task_struct *task;
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struct inode *inode;
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unsigned int fd;
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if (flags & LOOKUP_RCU)
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return -ECHILD;
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inode = d_inode(dentry);
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task = get_proc_task(inode);
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fd = proc_fd(inode);
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if (task) {
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fmode_t f_mode;
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if (tid_fd_mode(task, fd, &f_mode)) {
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tid_fd_update_inode(task, inode, f_mode);
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put_task_struct(task);
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return 1;
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}
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put_task_struct(task);
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}
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return 0;
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}
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static const struct dentry_operations tid_fd_dentry_operations = {
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.d_revalidate = tid_fd_revalidate,
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.d_delete = pid_delete_dentry,
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};
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static int proc_fd_link(struct dentry *dentry, struct path *path)
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{
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struct task_struct *task;
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int ret = -ENOENT;
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task = get_proc_task(d_inode(dentry));
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if (task) {
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unsigned int fd = proc_fd(d_inode(dentry));
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struct file *fd_file;
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fd_file = fget_task(task, fd);
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if (fd_file) {
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*path = fd_file->f_path;
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path_get(&fd_file->f_path);
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ret = 0;
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fput(fd_file);
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}
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put_task_struct(task);
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}
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return ret;
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}
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struct fd_data {
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fmode_t mode;
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unsigned fd;
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};
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static struct dentry *proc_fd_instantiate(struct dentry *dentry,
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struct task_struct *task, const void *ptr)
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{
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const struct fd_data *data = ptr;
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struct proc_inode *ei;
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struct inode *inode;
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inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK);
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if (!inode)
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return ERR_PTR(-ENOENT);
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ei = PROC_I(inode);
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ei->fd = data->fd;
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inode->i_op = &proc_pid_link_inode_operations;
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inode->i_size = 64;
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ei->op.proc_get_link = proc_fd_link;
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tid_fd_update_inode(task, inode, data->mode);
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d_set_d_op(dentry, &tid_fd_dentry_operations);
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return d_splice_alias(inode, dentry);
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}
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static struct dentry *proc_lookupfd_common(struct inode *dir,
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struct dentry *dentry,
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instantiate_t instantiate)
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{
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struct task_struct *task = get_proc_task(dir);
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struct fd_data data = {.fd = name_to_int(&dentry->d_name)};
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struct dentry *result = ERR_PTR(-ENOENT);
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if (!task)
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goto out_no_task;
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if (data.fd == ~0U)
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goto out;
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if (!tid_fd_mode(task, data.fd, &data.mode))
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goto out;
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result = instantiate(dentry, task, &data);
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out:
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put_task_struct(task);
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out_no_task:
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return result;
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}
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static int proc_readfd_common(struct file *file, struct dir_context *ctx,
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instantiate_t instantiate)
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{
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struct task_struct *p = get_proc_task(file_inode(file));
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unsigned int fd;
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if (!p)
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return -ENOENT;
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if (!dir_emit_dots(file, ctx))
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goto out;
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rcu_read_lock();
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for (fd = ctx->pos - 2;; fd++) {
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struct file *f;
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struct fd_data data;
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char name[10 + 1];
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unsigned int len;
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f = task_lookup_next_fd_rcu(p, &fd);
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ctx->pos = fd + 2LL;
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if (!f)
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break;
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data.mode = f->f_mode;
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rcu_read_unlock();
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data.fd = fd;
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len = snprintf(name, sizeof(name), "%u", fd);
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if (!proc_fill_cache(file, ctx,
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name, len, instantiate, p,
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&data))
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goto out;
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cond_resched();
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rcu_read_lock();
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}
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rcu_read_unlock();
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out:
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put_task_struct(p);
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return 0;
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}
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static int proc_readfd_count(struct inode *inode, loff_t *count)
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{
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struct task_struct *p = get_proc_task(inode);
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struct fdtable *fdt;
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if (!p)
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return -ENOENT;
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task_lock(p);
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if (p->files) {
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rcu_read_lock();
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fdt = files_fdtable(p->files);
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*count = bitmap_weight(fdt->open_fds, fdt->max_fds);
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rcu_read_unlock();
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}
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task_unlock(p);
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put_task_struct(p);
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return 0;
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}
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static int proc_readfd(struct file *file, struct dir_context *ctx)
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{
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return proc_readfd_common(file, ctx, proc_fd_instantiate);
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}
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const struct file_operations proc_fd_operations = {
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.read = generic_read_dir,
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.iterate_shared = proc_readfd,
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.llseek = generic_file_llseek,
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};
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static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
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unsigned int flags)
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{
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return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
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}
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/*
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* /proc/pid/fd needs a special permission handler so that a process can still
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* access /proc/self/fd after it has executed a setuid().
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*/
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int proc_fd_permission(struct mnt_idmap *idmap,
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struct inode *inode, int mask)
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{
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struct task_struct *p;
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int rv;
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rv = generic_permission(&nop_mnt_idmap, inode, mask);
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if (rv == 0)
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return rv;
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rcu_read_lock();
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p = pid_task(proc_pid(inode), PIDTYPE_PID);
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if (p && same_thread_group(p, current))
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rv = 0;
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rcu_read_unlock();
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return rv;
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}
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static int proc_fd_getattr(struct mnt_idmap *idmap,
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const struct path *path, struct kstat *stat,
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u32 request_mask, unsigned int query_flags)
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{
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struct inode *inode = d_inode(path->dentry);
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int rv = 0;
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generic_fillattr(&nop_mnt_idmap, inode, stat);
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/* If it's a directory, put the number of open fds there */
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if (S_ISDIR(inode->i_mode)) {
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rv = proc_readfd_count(inode, &stat->size);
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if (rv < 0)
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return rv;
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}
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return rv;
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}
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const struct inode_operations proc_fd_inode_operations = {
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.lookup = proc_lookupfd,
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.permission = proc_fd_permission,
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.getattr = proc_fd_getattr,
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.setattr = proc_setattr,
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};
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static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
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struct task_struct *task, const void *ptr)
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{
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const struct fd_data *data = ptr;
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struct proc_inode *ei;
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struct inode *inode;
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inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO);
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if (!inode)
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return ERR_PTR(-ENOENT);
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ei = PROC_I(inode);
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ei->fd = data->fd;
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inode->i_fop = &proc_fdinfo_file_operations;
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tid_fd_update_inode(task, inode, 0);
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d_set_d_op(dentry, &tid_fd_dentry_operations);
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return d_splice_alias(inode, dentry);
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}
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static struct dentry *
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proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
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{
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return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
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}
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static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
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{
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return proc_readfd_common(file, ctx,
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proc_fdinfo_instantiate);
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}
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static int proc_open_fdinfo(struct inode *inode, struct file *file)
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{
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int ret = proc_fdinfo_access_allowed(inode);
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if (ret)
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return ret;
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return 0;
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}
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const struct inode_operations proc_fdinfo_inode_operations = {
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.lookup = proc_lookupfdinfo,
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.setattr = proc_setattr,
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};
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const struct file_operations proc_fdinfo_operations = {
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.open = proc_open_fdinfo,
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.read = generic_read_dir,
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.iterate_shared = proc_readfdinfo,
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.llseek = generic_file_llseek,
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};
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