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Commit 8280d161 authored by Al Viro's avatar Al Viro
Browse files

new helper: replace_fd() 



analog of dup2(), except that it takes struct file * as source.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent fe17f22d

fs/exec.c

+1 −10
Original line number Diff line number Diff line
@@ -2041,23 +2041,14 @@ static void wait_for_dump_helpers(struct file *file) 
static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)

{

	struct file *files[2];

	struct fdtable *fdt;

	struct coredump_params *cp = (struct coredump_params *)info->data;

	struct files_struct *cf = current->files;

	int err = create_pipe_files(files, 0);

	if (err)

		return err;



	cp->file = files[1];



	sys_close(0);

	fd_install(0, files[0]);

	spin_lock(&cf->file_lock);

	fdt = files_fdtable(cf);

	__set_open_fd(0, fdt);

	__clear_close_on_exec(0, fdt);

	spin_unlock(&cf->file_lock);



	replace_fd(0, files[0], 0);

	/* and disallow core files too */

	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};

fs/file.c

+62 −29
Original line number Diff line number Diff line
@@ -821,29 +821,12 @@ bool get_close_on_exec(unsigned int fd) 
	return res;

}



SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)

static int do_dup2(struct files_struct *files,

	struct file *file, unsigned fd, unsigned flags)

{

	int err = -EBADF;

	struct file * file, *tofree;

	struct files_struct * files = current->files;

	struct file *tofree;

	struct fdtable *fdt;



	if ((flags & ~O_CLOEXEC) != 0)

		return -EINVAL;



	if (newfd >= rlimit(RLIMIT_NOFILE))

		return -EMFILE;



	spin_lock(&files->file_lock);

	err = expand_files(files, newfd);

	file = fcheck(oldfd);

	if (unlikely(!file))

		goto Ebadf;

	if (unlikely(err < 0)) {

		if (err == -EMFILE)

			goto Ebadf;

		goto out_unlock;

	}

	/*

	 * We need to detect attempts to do dup2() over allocated but still

	 * not finished descriptor.  NB: OpenBSD avoids that at the price of
@@ -858,24 +841,74 @@ SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) 
	 * scope of POSIX or SUS, since neither considers shared descriptor

	 * tables and this condition does not arise without those.

	 */

	err = -EBUSY;

	fdt = files_fdtable(files);

	tofree = fdt->fd[newfd];

	if (!tofree && fd_is_open(newfd, fdt))

		goto out_unlock;

	tofree = fdt->fd[fd];

	if (!tofree && fd_is_open(fd, fdt))

		goto Ebusy;

	get_file(file);

	rcu_assign_pointer(fdt->fd[newfd], file);

	__set_open_fd(newfd, fdt);

	rcu_assign_pointer(fdt->fd[fd], file);

	__set_open_fd(fd, fdt);

	if (flags & O_CLOEXEC)

		__set_close_on_exec(newfd, fdt);

		__set_close_on_exec(fd, fdt);

	else

		__clear_close_on_exec(newfd, fdt);

		__clear_close_on_exec(fd, fdt);

	spin_unlock(&files->file_lock);



	if (tofree)

		filp_close(tofree, files);



	return newfd;

	return fd;



Ebusy:

	spin_unlock(&files->file_lock);

	return -EBUSY;

}



int replace_fd(unsigned fd, struct file *file, unsigned flags)

{

	int err;

	struct files_struct *files = current->files;



	if (!file)

		return __close_fd(files, fd);



	if (fd >= rlimit(RLIMIT_NOFILE))

		return -EMFILE;



	spin_lock(&files->file_lock);

	err = expand_files(files, fd);

	if (unlikely(err < 0))

		goto out_unlock;

	return do_dup2(files, file, fd, flags);



out_unlock:

	spin_unlock(&files->file_lock);

	return err;

}



SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)

{

	int err = -EBADF;

	struct file *file;

	struct files_struct *files = current->files;



	if ((flags & ~O_CLOEXEC) != 0)

		return -EINVAL;



	if (newfd >= rlimit(RLIMIT_NOFILE))

		return -EMFILE;



	spin_lock(&files->file_lock);

	err = expand_files(files, newfd);

	file = fcheck(oldfd);

	if (unlikely(!file))

		goto Ebadf;

	if (unlikely(err < 0)) {

		if (err == -EMFILE)

			goto Ebadf;

		goto out_unlock;

	}

	return do_dup2(files, file, newfd, flags);



Ebadf:

	err = -EBADF;

include/linux/file.h

+1 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ extern struct file *fget_light(unsigned int fd, int *fput_needed); 
extern struct file *fget_raw(unsigned int fd);

extern struct file *fget_raw_light(unsigned int fd, int *fput_needed);

extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);

extern int replace_fd(unsigned fd, struct file *file, unsigned flags);

extern void set_close_on_exec(unsigned int fd, int flag);

extern bool get_close_on_exec(unsigned int fd);

extern void put_filp(struct file *);