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Commit f8f95702 authored by Al Viro's avatar Al Viro
Browse files

[PATCH] sanitize locate_fd() 



* 'file' argument is unused; lose it.
* move setting flags from the caller (dupfd()) to locate_fd();
  pass cloexec flag as new argument.  Note that files_fdtable()
  that used to be in dupfd() isn't needed in the place in
  locate_fd() where the moved code ends up - we know that ->file_lock
  hadn't been dropped since the last time we calculated fdt because
  we can get there only if expand_files() returns 0 and it doesn't
  drop/reacquire in that case.
* move getting/dropping ->file_lock into locate_fd().  Now the caller
  doesn't need to do anything with files_struct *files anymore and
  we can move that inside locate_fd() as well, killing the
  struct files_struct * argument.

At that point locate_fd() is extremely similar to get_unused_fd_flags()
and the next patches will merge those two.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 3b125388

fs/fcntl.c

+14 −26
Original line number Diff line number Diff line
@@ -55,14 +55,16 @@ static int get_close_on_exec(unsigned int fd) 
 * file_lock held for write.

 */



static int locate_fd(struct files_struct *files, 

			    struct file *file, unsigned int orig_start)

static int locate_fd(unsigned int orig_start, int cloexec)

{

	struct files_struct *files = current->files;

	unsigned int newfd;

	unsigned int start;

	int error;

	struct fdtable *fdt;



	spin_lock(&files->file_lock);



	error = -EINVAL;

	if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)

		goto out;
@@ -97,42 +99,28 @@ repeat: 
	if (error)

		goto repeat;



	/*

	 * We reacquired files_lock, so we are safe as long as

	 * we reacquire the fdtable pointer and use it while holding

	 * the lock, no one can free it during that time.

	 */

	if (start <= files->next_fd)

		files->next_fd = newfd + 1;



	FD_SET(newfd, fdt->open_fds);

	if (cloexec)

		FD_SET(newfd, fdt->close_on_exec);

	else

		FD_CLR(newfd, fdt->close_on_exec);

	error = newfd;



out:

	spin_unlock(&files->file_lock);

	return error;

}



static int dupfd(struct file *file, unsigned int start, int cloexec)

{

	struct files_struct * files = current->files;

	struct fdtable *fdt;

	int fd;



	spin_lock(&files->file_lock);

	fd = locate_fd(files, file, start);

	if (fd >= 0) {

		/* locate_fd() may have expanded fdtable, load the ptr */

		fdt = files_fdtable(files);

		FD_SET(fd, fdt->open_fds);

		if (cloexec)

			FD_SET(fd, fdt->close_on_exec);

		else

			FD_CLR(fd, fdt->close_on_exec);

		spin_unlock(&files->file_lock);

	int fd = locate_fd(start, cloexec);

	if (fd >= 0)

		fd_install(fd, file);

	} else {

		spin_unlock(&files->file_lock);

	else

		fput(file);

	}



	return fd;

}