[RFC PATCH 16/35] syscalls: do not call sys_dup{,3}() within the kernel

[Dominik Brodowski]

CC: Alexander Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net>
---
 fs/file.c                | 16 +++++++++++++---
 include/linux/syscalls.h |  1 +
 init/do_mounts_initrd.c  |  4 ++--
 init/main.c              |  4 ++--
 4 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index 42f0db4bd0fb..d304004f0b65 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -870,7 +870,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned 
flags)
        return err;
 }
 
-SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
+static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 {
        int err = -EBADF;
        struct file *file;
@@ -904,6 +904,11 @@ SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, 
newfd, int, flags)
        return err;
 }
 
+SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
+{
+       return ksys_dup3(oldfd, newfd, flags);
+}
+
 SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 {
        if (unlikely(newfd == oldfd)) { /* corner case */
@@ -916,10 +921,10 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, 
newfd)
                rcu_read_unlock();
                return retval;
        }
-       return sys_dup3(oldfd, newfd, 0);
+       return ksys_dup3(oldfd, newfd, 0);
 }
 
-SYSCALL_DEFINE1(dup, unsigned int, fildes)
+int ksys_dup(unsigned int fildes)
 {
        int ret = -EBADF;
        struct file *file = fget_raw(fildes);
@@ -934,6 +939,11 @@ SYSCALL_DEFINE1(dup, unsigned int, fildes)
        return ret;
 }
 
+SYSCALL_DEFINE1(dup, unsigned int, fildes)
+{
+       return ksys_dup(fildes);
+}
+
 int f_dupfd(unsigned int from, struct file *file, unsigned flags)
 {
        int err;
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index d509f4992d2e..986e91d5a2ea 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -951,5 +951,6 @@ asmlinkage long sys_statx(int dfd, const char __user *path, 
unsigned flags,
 int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
               unsigned long flags, void __user *data);
 int ksys_umount(char __user *name, int flags);
+int ksys_dup(unsigned int fildes);
 
 #endif
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 1c4da8353332..e8573e1776f6 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -39,8 +39,8 @@ static int init_linuxrc(struct subprocess_info *info, struct 
cred *new)
        sys_unshare(CLONE_FS | CLONE_FILES);
        /* stdin/stdout/stderr for /linuxrc */
        sys_open("/dev/console", O_RDWR, 0);
-       sys_dup(0);
-       sys_dup(0);
+       ksys_dup(0);
+       ksys_dup(0);
        /* move initrd over / and chdir/chroot in initrd root */
        sys_chdir("/root");
        ksys_mount(".", "/", NULL, MS_MOVE, NULL);
diff --git a/init/main.c b/init/main.c
index 969eaf140ef0..b8649d1466e1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1077,8 +1077,8 @@ static noinline void __init kernel_init_freeable(void)
        if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
                pr_err("Warning: unable to open an initial console.\n");
 
-       (void) sys_dup(0);
-       (void) sys_dup(0);
+       (void) ksys_dup(0);
+       (void) ksys_dup(0);
        /*
         * check if there is an early userspace init.  If yes, let it do all
         * the work
-- 
2.16.2