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![Christian Brauner](/assets/img/avatar_default.png)
The may_follow_link(), may_linkat(), may_lookup(), may_open(), may_o_create(), may_create_in_sticky(), may_delete(), and may_create() helpers determine whether the caller is privileged enough to perform the associated operations. Let them handle idmapped mounts by mapping the inode or fsids according to the mount's user namespace. Afterwards the checks are identical to non-idmapped inodes. The patch takes care to retrieve the mount's user namespace right before performing permission checks and passing it down into the fileystem so the user namespace can't change in between by someone idmapping a mount that is currently not idmapped. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-13-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
265 lines
5.9 KiB
C
265 lines
5.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Routines that mimic syscalls, but don't use the user address space or file
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* descriptors. Only for init/ and related early init code.
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*/
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#include <linux/init.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/fs.h>
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#include <linux/fs_struct.h>
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#include <linux/file.h>
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#include <linux/init_syscalls.h>
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#include <linux/security.h>
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#include "internal.h"
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int __init init_mount(const char *dev_name, const char *dir_name,
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const char *type_page, unsigned long flags, void *data_page)
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{
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struct path path;
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int ret;
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ret = kern_path(dir_name, LOOKUP_FOLLOW, &path);
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if (ret)
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return ret;
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ret = path_mount(dev_name, &path, type_page, flags, data_page);
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path_put(&path);
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return ret;
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}
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int __init init_umount(const char *name, int flags)
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{
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int lookup_flags = LOOKUP_MOUNTPOINT;
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struct path path;
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int ret;
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if (!(flags & UMOUNT_NOFOLLOW))
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lookup_flags |= LOOKUP_FOLLOW;
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ret = kern_path(name, lookup_flags, &path);
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if (ret)
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return ret;
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return path_umount(&path, flags);
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}
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int __init init_chdir(const char *filename)
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{
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struct path path;
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int error;
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error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
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if (error)
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return error;
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error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
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if (!error)
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set_fs_pwd(current->fs, &path);
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path_put(&path);
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return error;
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}
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int __init init_chroot(const char *filename)
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{
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struct path path;
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int error;
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error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
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if (error)
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return error;
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error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
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if (error)
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goto dput_and_out;
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error = -EPERM;
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if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
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goto dput_and_out;
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error = security_path_chroot(&path);
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if (error)
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goto dput_and_out;
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set_fs_root(current->fs, &path);
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dput_and_out:
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path_put(&path);
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return error;
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}
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int __init init_chown(const char *filename, uid_t user, gid_t group, int flags)
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{
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int lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
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struct path path;
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int error;
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error = kern_path(filename, lookup_flags, &path);
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if (error)
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return error;
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error = mnt_want_write(path.mnt);
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if (!error) {
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error = chown_common(&path, user, group);
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mnt_drop_write(path.mnt);
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}
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path_put(&path);
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return error;
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}
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int __init init_chmod(const char *filename, umode_t mode)
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{
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struct path path;
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int error;
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error = kern_path(filename, LOOKUP_FOLLOW, &path);
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if (error)
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return error;
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error = chmod_common(&path, mode);
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path_put(&path);
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return error;
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}
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int __init init_eaccess(const char *filename)
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{
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struct path path;
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int error;
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error = kern_path(filename, LOOKUP_FOLLOW, &path);
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if (error)
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return error;
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error = path_permission(&path, MAY_ACCESS);
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path_put(&path);
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return error;
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}
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int __init init_stat(const char *filename, struct kstat *stat, int flags)
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{
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int lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
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struct path path;
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int error;
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error = kern_path(filename, lookup_flags, &path);
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if (error)
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return error;
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error = vfs_getattr(&path, stat, STATX_BASIC_STATS,
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flags | AT_NO_AUTOMOUNT);
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path_put(&path);
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return error;
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}
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int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
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{
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struct dentry *dentry;
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struct path path;
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int error;
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if (S_ISFIFO(mode) || S_ISSOCK(mode))
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dev = 0;
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else if (!(S_ISBLK(mode) || S_ISCHR(mode)))
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return -EINVAL;
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dentry = kern_path_create(AT_FDCWD, filename, &path, 0);
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if (IS_ERR(dentry))
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return PTR_ERR(dentry);
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if (!IS_POSIXACL(path.dentry->d_inode))
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mode &= ~current_umask();
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error = security_path_mknod(&path, dentry, mode, dev);
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if (!error)
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error = vfs_mknod(path.dentry->d_inode, dentry, mode,
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new_decode_dev(dev));
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done_path_create(&path, dentry);
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return error;
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}
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int __init init_link(const char *oldname, const char *newname)
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{
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struct dentry *new_dentry;
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struct path old_path, new_path;
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int error;
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error = kern_path(oldname, 0, &old_path);
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if (error)
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return error;
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new_dentry = kern_path_create(AT_FDCWD, newname, &new_path, 0);
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error = PTR_ERR(new_dentry);
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if (IS_ERR(new_dentry))
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goto out;
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error = -EXDEV;
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if (old_path.mnt != new_path.mnt)
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goto out_dput;
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error = may_linkat(&init_user_ns, &old_path);
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if (unlikely(error))
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goto out_dput;
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error = security_path_link(old_path.dentry, &new_path, new_dentry);
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if (error)
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goto out_dput;
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error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry,
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NULL);
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out_dput:
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done_path_create(&new_path, new_dentry);
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out:
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path_put(&old_path);
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return error;
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}
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int __init init_symlink(const char *oldname, const char *newname)
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{
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struct dentry *dentry;
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struct path path;
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int error;
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dentry = kern_path_create(AT_FDCWD, newname, &path, 0);
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if (IS_ERR(dentry))
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return PTR_ERR(dentry);
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error = security_path_symlink(&path, dentry, oldname);
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if (!error)
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error = vfs_symlink(path.dentry->d_inode, dentry, oldname);
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done_path_create(&path, dentry);
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return error;
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}
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int __init init_unlink(const char *pathname)
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{
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return do_unlinkat(AT_FDCWD, getname_kernel(pathname));
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}
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int __init init_mkdir(const char *pathname, umode_t mode)
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{
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struct dentry *dentry;
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struct path path;
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int error;
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dentry = kern_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
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if (IS_ERR(dentry))
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return PTR_ERR(dentry);
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if (!IS_POSIXACL(path.dentry->d_inode))
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mode &= ~current_umask();
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error = security_path_mkdir(&path, dentry, mode);
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if (!error)
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error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
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done_path_create(&path, dentry);
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return error;
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}
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int __init init_rmdir(const char *pathname)
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{
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return do_rmdir(AT_FDCWD, getname_kernel(pathname));
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}
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int __init init_utimes(char *filename, struct timespec64 *ts)
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{
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struct path path;
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int error;
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error = kern_path(filename, 0, &path);
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if (error)
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return error;
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error = vfs_utimes(&path, ts);
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path_put(&path);
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return error;
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}
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int __init init_dup(struct file *file)
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{
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int fd;
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fd = get_unused_fd_flags(0);
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if (fd < 0)
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return fd;
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fd_install(fd, get_file(file));
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return 0;
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}
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