[PATCH 12/21] init: add an init_chroot helper
From: Christoph Hellwig <hch@lst.de>
Date: 2020-07-26 07:14:32
Also in:
linux-fsdevel, linux-raid, lkml
Subsystem:
abi/api, driver core, kobjects, debugfs and sysfs, filesystems (vfs and infrastructure), the rest · Maintainers:
Greg Kroah-Hartman, "Rafael J. Wysocki", Danilo Krummrich, Alexander Viro, Christian Brauner, Linus Torvalds
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> --- drivers/base/devtmpfs.c | 2 +- fs/for_init.c | 24 ++++++++++++++++++++++++ fs/open.c | 7 +------ include/linux/init_syscalls.h | 1 + include/linux/syscalls.h | 2 -- init/do_mounts.c | 2 +- init/do_mounts_initrd.c | 4 ++-- 7 files changed, 30 insertions(+), 12 deletions(-)
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index bc2cfe10018cd5..36e81b52368650 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c@@ -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);
diff --git a/fs/for_init.c b/fs/for_init.c
index e5d907d4b98aac..2d5428b7dc1420 100644
--- a/fs/for_init.c
+++ b/fs/for_init.c@@ -5,6 +5,7 @@ #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,
@@ -50,6 +51,29 @@ 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));
diff --git a/fs/open.c b/fs/open.c
index 723e0ac898935e..f62f4752bb436d 100644
--- a/fs/open.c
+++ b/fs/open.c@@ -530,7 +530,7 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd) 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 @@ int ksys_chroot(const char __user *filename) 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;
diff --git a/include/linux/init_syscalls.h b/include/linux/init_syscalls.h
index 1e845910ae56e9..e07099a14b91db 100644
--- a/include/linux/init_syscalls.h
+++ b/include/linux/init_syscalls.h@@ -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);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 31fa67fb9894b3..e89d62e944dc0e 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h@@ -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);
diff --git a/init/do_mounts.c b/init/do_mounts.c
index cc08ed7b44e764..c8ccdc80ffcdd5 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c@@ -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;
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 04627fd22a921f..a6b447b191dbc8 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c@@ -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");
--
2.27.0