linux-stable/fs/init.c
Christian Brauner 4609e1f18e
fs: port ->permission() to pass mnt_idmap
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>
2023-01-19 09:24:28 +01:00

269 lines
6 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Routines that mimic syscalls, but don't use the user address space or file
* descriptors. Only for init/ and related early init code.
*/
#include <linux/init.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/fs.h>
#include <linux/fs_struct.h>
#include <linux/file.h>
#include <linux/init_syscalls.h>
#include <linux/security.h>
#include "internal.h"
int __init init_mount(const char *dev_name, const char *dir_name,
const char *type_page, unsigned long flags, void *data_page)
{
struct path path;
int ret;
ret = kern_path(dir_name, LOOKUP_FOLLOW, &path);
if (ret)
return ret;
ret = path_mount(dev_name, &path, type_page, flags, data_page);
path_put(&path);
return ret;
}
int __init init_umount(const char *name, int flags)
{
int lookup_flags = LOOKUP_MOUNTPOINT;
struct path path;
int ret;
if (!(flags & UMOUNT_NOFOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
ret = kern_path(name, lookup_flags, &path);
if (ret)
return ret;
return path_umount(&path, flags);
}
int __init init_chdir(const char *filename)
{
struct path path;
int error;
error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
if (error)
return error;
error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
if (!error)
set_fs_pwd(current->fs, &path);
path_put(&path);
return error;
}
int __init init_chroot(const char *filename)
{
struct path path;
int error;
error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
if (error)
return error;
error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
if (error)
goto dput_and_out;
error = -EPERM;
if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
goto dput_and_out;
error = security_path_chroot(&path);
if (error)
goto dput_and_out;
set_fs_root(current->fs, &path);
dput_and_out:
path_put(&path);
return error;
}
int __init init_chown(const char *filename, uid_t user, gid_t group, int flags)
{
int lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
struct path path;
int error;
error = kern_path(filename, lookup_flags, &path);
if (error)
return error;
error = mnt_want_write(path.mnt);
if (!error) {
error = chown_common(&path, user, group);
mnt_drop_write(path.mnt);
}
path_put(&path);
return error;
}
int __init init_chmod(const char *filename, umode_t mode)
{
struct path path;
int error;
error = kern_path(filename, LOOKUP_FOLLOW, &path);
if (error)
return error;
error = chmod_common(&path, mode);
path_put(&path);
return error;
}
int __init init_eaccess(const char *filename)
{
struct path path;
int error;
error = kern_path(filename, LOOKUP_FOLLOW, &path);
if (error)
return error;
error = path_permission(&path, MAY_ACCESS);
path_put(&path);
return error;
}
int __init init_stat(const char *filename, struct kstat *stat, int flags)
{
int lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
struct path path;
int error;
error = kern_path(filename, lookup_flags, &path);
if (error)
return error;
error = vfs_getattr(&path, stat, STATX_BASIC_STATS,
flags | AT_NO_AUTOMOUNT);
path_put(&path);
return error;
}
int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
{
struct dentry *dentry;
struct path path;
int error;
if (S_ISFIFO(mode) || S_ISSOCK(mode))
dev = 0;
else if (!(S_ISBLK(mode) || S_ISCHR(mode)))
return -EINVAL;
dentry = kern_path_create(AT_FDCWD, filename, &path, 0);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (!IS_POSIXACL(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mknod(&path, dentry, mode, dev);
if (!error)
error = vfs_mknod(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, mode, new_decode_dev(dev));
done_path_create(&path, dentry);
return error;
}
int __init init_link(const char *oldname, const char *newname)
{
struct dentry *new_dentry;
struct path old_path, new_path;
struct mnt_idmap *idmap;
int error;
error = kern_path(oldname, 0, &old_path);
if (error)
return error;
new_dentry = kern_path_create(AT_FDCWD, newname, &new_path, 0);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto out;
error = -EXDEV;
if (old_path.mnt != new_path.mnt)
goto out_dput;
idmap = mnt_idmap(new_path.mnt);
error = may_linkat(idmap, &old_path);
if (unlikely(error))
goto out_dput;
error = security_path_link(old_path.dentry, &new_path, new_dentry);
if (error)
goto out_dput;
error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode,
new_dentry, NULL);
out_dput:
done_path_create(&new_path, new_dentry);
out:
path_put(&old_path);
return error;
}
int __init init_symlink(const char *oldname, const char *newname)
{
struct dentry *dentry;
struct path path;
int error;
dentry = kern_path_create(AT_FDCWD, newname, &path, 0);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
error = security_path_symlink(&path, dentry, oldname);
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, oldname);
done_path_create(&path, dentry);
return error;
}
int __init init_unlink(const char *pathname)
{
return do_unlinkat(AT_FDCWD, getname_kernel(pathname));
}
int __init init_mkdir(const char *pathname, umode_t mode)
{
struct dentry *dentry;
struct path path;
int error;
dentry = kern_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (!IS_POSIXACL(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mkdir(&path, dentry, mode);
if (!error)
error = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, mode);
done_path_create(&path, dentry);
return error;
}
int __init init_rmdir(const char *pathname)
{
return do_rmdir(AT_FDCWD, getname_kernel(pathname));
}
int __init init_utimes(char *filename, struct timespec64 *ts)
{
struct path path;
int error;
error = kern_path(filename, 0, &path);
if (error)
return error;
error = vfs_utimes(&path, ts);
path_put(&path);
return error;
}
int __init init_dup(struct file *file)
{
int fd;
fd = get_unused_fd_flags(0);
if (fd < 0)
return fd;
fd_install(fd, get_file(file));
return 0;
}