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    Subject[RFC PATCH 16/35] syscalls: do not call sys_dup{,3}() within the kernel
    Date
    CC: Alexander Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Dominik Brodowski <linux@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
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