init: add an init_chroot helper

Add a simple helper to chroot with a kernel space file name and switch
the early init code over to it.  Remove the now unused ksys_chroot.

Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Christoph Hellwig 2020-07-22 11:26:13 +02:00
parent db63f1e315
commit 4b7ca5014c
7 changed files with 30 additions and 12 deletions

View File

@ -413,7 +413,7 @@ static int __init devtmpfs_setup(void *p)
if (err)
goto out;
init_chdir("/.."); /* will traverse into overmounted root */
ksys_chroot(".");
init_chroot(".");
out:
*(int *)p = err;
complete(&setup_done);

View File

@ -9,6 +9,7 @@
#include <linux/fs.h>
#include <linux/fs_struct.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,
@ -54,6 +55,29 @@ int __init init_chdir(const char *filename)
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 = inode_permission(path.dentry->d_inode, 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_unlink(const char *pathname)
{
return do_unlinkat(AT_FDCWD, getname_kernel(pathname));

View File

@ -530,7 +530,7 @@ out:
return error;
}
int ksys_chroot(const char __user *filename)
SYSCALL_DEFINE1(chroot, const char __user *, filename)
{
struct path path;
int error;
@ -563,11 +563,6 @@ out:
return error;
}
SYSCALL_DEFINE1(chroot, const char __user *, filename)
{
return ksys_chroot(filename);
}
static int chmod_common(const struct path *path, umode_t mode)
{
struct inode *inode = path->dentry->d_inode;

View File

@ -4,5 +4,6 @@ int __init init_mount(const char *dev_name, const char *dir_name,
const char *type_page, unsigned long flags, void *data_page);
int __init init_umount(const char *name, int flags);
int __init init_chdir(const char *filename);
int __init init_chroot(const char *filename);
int __init init_unlink(const char *pathname);
int __init init_rmdir(const char *pathname);

View File

@ -1235,8 +1235,6 @@ asmlinkage long sys_ni_syscall(void);
* Instead, use one of the functions which work equivalently, such as
* the ksys_xyzyyz() functions prototyped below.
*/
int ksys_chroot(const char __user *filename);
ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);
int ksys_fchown(unsigned int fd, uid_t user, gid_t group);
ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count);

View File

@ -629,7 +629,7 @@ void __init prepare_namespace(void)
out:
devtmpfs_mount();
init_mount(".", "/", NULL, MS_MOVE, NULL);
ksys_chroot(".");
init_chroot(".");
}
static bool is_tmpfs;

View File

@ -63,7 +63,7 @@ static int __init init_linuxrc(struct subprocess_info *info, struct cred *new)
/* move initrd over / and chdir/chroot in initrd root */
init_chdir("/root");
init_mount(".", "/", NULL, MS_MOVE, NULL);
ksys_chroot(".");
init_chroot(".");
ksys_setsid();
return 0;
}
@ -101,7 +101,7 @@ static void __init handle_initrd(void)
/* move initrd to rootfs' /old */
init_mount("..", ".", NULL, MS_MOVE, NULL);
/* switch root and cwd back to / of rootfs */
ksys_chroot("..");
init_chroot("..");
if (new_decode_dev(real_root_dev) == Root_RAM0) {
init_chdir("/old");