[PATCH 07/24] fs: add a kern_chroot helper
From: Christoph Hellwig <hch@lst.de>
Date: 2020-07-20 15:59:20
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 for a chroot with a kernelspace name and use it in the early init code instead of relying on the implicit set_fs(KERNEL_DS) there. Remove the now unused ksys_chroot. Signed-off-by: Christoph Hellwig <hch@lst.de> --- drivers/base/devtmpfs.c | 2 +- fs/open.c | 15 ++++++++++----- include/linux/fs.h | 1 + include/linux/syscalls.h | 1 - init/do_mounts.c | 2 +- init/do_mounts_initrd.c | 4 ++-- 6 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 2cedeb62706f18..a5126e7be34c8a 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c@@ -389,7 +389,7 @@ static int devtmpfs_setup(void *p) if (err) goto out; kern_chdir("/.."); /* will traverse into overmounted root */ - ksys_chroot("."); + kern_chroot("."); out: *(int *)p = err; complete(&setup_done);
diff --git a/fs/open.c b/fs/open.c
index 3d62f4d2604739..424db905da5f18 100644
--- a/fs/open.c
+++ b/fs/open.c@@ -540,15 +540,15 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd) return error; } -int ksys_chroot(const char __user *filename) +static int do_chroot(struct filename *name) { struct path path; int error; unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY; retry: - error = user_path_at(AT_FDCWD, filename, lookup_flags, &path); + error = filename_lookup(AT_FDCWD, name, lookup_flags, &path, NULL); if (error) - goto out; + return error; error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR); if (error)
@@ -569,13 +569,18 @@ int ksys_chroot(const char __user *filename) lookup_flags |= LOOKUP_REVAL; goto retry; } -out: + putname(name); return error; } +int kern_chroot(const char *filename) +{ + return do_chroot(getname_kernel(filename)); +} + SYSCALL_DEFINE1(chroot, const char __user *, filename) { - return ksys_chroot(filename); + return do_chroot(getname(filename)); } static int chmod_common(const struct path *path, umode_t mode)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index dccb37407e9bad..0205355bffb1bc 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h@@ -3672,5 +3672,6 @@ static inline int inode_drain_writes(struct inode *inode) } int kern_chdir(const char *filename); +int kern_chroot(const char *filename); #endif /* _LINUX_FS_H */
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index f2a181776b0409..a3176d1a521467 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h@@ -1236,7 +1236,6 @@ asmlinkage long sys_ni_syscall(void); * 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 8c3fca8e2d3c6e..31b8dedb189b57 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c@@ -629,7 +629,7 @@ void __init prepare_namespace(void) out: devtmpfs_mount(); do_kern_mount(".", "/", NULL, MS_MOVE, NULL); - ksys_chroot("."); + kern_chroot("."); } static bool is_tmpfs;
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 522554d703b785..1cbc9988d2e0ad 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 */ kern_chdir("/root"); do_kern_mount(".", "/", NULL, MS_MOVE, NULL); - ksys_chroot("."); + kern_chroot("."); ksys_setsid(); return 0; }
@@ -101,7 +101,7 @@ static void __init handle_initrd(void) /* move initrd to rootfs' /old */ do_kern_mount("..", ".", NULL, MS_MOVE, NULL); /* switch root and cwd back to / of rootfs */ - ksys_chroot(".."); + kern_chroot(".."); if (new_decode_dev(real_root_dev) == Root_RAM0) { kern_chdir("/old");
--
2.27.0