[RFC PATCH 22/35] syscalls: do not call sys_chdir() within the kernel

[Dominik Brodowski]

CC: Al Viro <v...@zeniv.linux.org.uk>
CC: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net>
---
 drivers/base/devtmpfs.c  | 2 +-
 fs/open.c                | 7 ++++++-
 include/linux/syscalls.h | 1 +
 init/do_mounts.c         | 2 +-
 init/do_mounts_initrd.c  | 8 ++++----
 5 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index d6f37537275c..f7768077e817 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -386,7 +386,7 @@ static int devtmpfsd(void *p)
        *err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
        if (*err)
                goto out;
-       sys_chdir("/.."); /* will traverse into overmounted root */
+       ksys_chdir("/.."); /* will traverse into overmounted root */
        ksys_chroot(".");
        complete(&setup_done);
        while (1) {
diff --git a/fs/open.c b/fs/open.c
index 7a475e8a2e41..a19b8277c439 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -431,7 +431,7 @@ SYSCALL_DEFINE2(access, const char __user *, filename, int, 
mode)
        return sys_faccessat(AT_FDCWD, filename, mode);
 }
 
-SYSCALL_DEFINE1(chdir, const char __user *, filename)
+int ksys_chdir(const char __user *filename)
 {
        struct path path;
        int error;
@@ -457,6 +457,11 @@ SYSCALL_DEFINE1(chdir, const char __user *, filename)
        return error;
 }
 
+SYSCALL_DEFINE1(chdir, const char __user *, filename)
+{
+       return ksys_chdir(filename);
+}
+
 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 {
        struct fd f = fdget_raw(fd);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 197c622d0b9f..03c70fa26852 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -959,5 +959,6 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, 
int advice);
 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
                              unsigned long prot, unsigned long flags,
                              unsigned long fd, unsigned long pgoff);
+int ksys_chdir(const char __user *filename);
 
 #endif
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 2f06f7827b0c..89f18985fa90 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -367,7 +367,7 @@ static int __init do_mount_root(char *name, char *fs, int 
flags, void *data)
        if (err)
                return err;
 
-       sys_chdir("/root");
+       ksys_chdir("/root");
        s = current->fs->pwd.dentry->d_sb;
        ROOT_DEV = s->s_dev;
        printk(KERN_INFO
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 414284dadc64..c19d9070134e 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -42,7 +42,7 @@ static int init_linuxrc(struct subprocess_info *info, struct 
cred *new)
        ksys_dup(0);
        ksys_dup(0);
        /* move initrd over / and chdir/chroot in initrd root */
-       sys_chdir("/root");
+       ksys_chdir("/root");
        ksys_mount(".", "/", NULL, MS_MOVE, NULL);
        ksys_chroot(".");
        sys_setsid();
@@ -61,7 +61,7 @@ static void __init handle_initrd(void)
        /* mount initrd on rootfs' /root */
        mount_block_root("/dev/root.old", root_mountflags & ~MS_RDONLY);
        sys_mkdir("/old", 0700);
-       sys_chdir("/old");
+       ksys_chdir("/old");
 
        /* try loading default modules from initrd */
        load_default_modules();
@@ -86,11 +86,11 @@ static void __init handle_initrd(void)
        ksys_chroot("..");
 
        if (new_decode_dev(real_root_dev) == Root_RAM0) {
-               sys_chdir("/old");
+               ksys_chdir("/old");
                return;
        }
 
-       sys_chdir("/");
+       ksys_chdir("/");
        ROOT_DEV = new_decode_dev(real_root_dev);
        mount_root();
 
-- 
2.16.2