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Commit a016f338 authored by JANAK DESAI's avatar JANAK DESAI Committed by Linus Torvalds
Browse files

[PATCH] unshare system call -v5: unshare files 



If the file descriptor structure is being shared, allocate a new one and copy
information from the current, shared, structure.

Signed-off-by: default avatarJanak Desai <janak@us.ibm.com>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Andi Kleen <ak@muc.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a0a7ec30

kernel/fork.c

+51 −30
Original line number Diff line number Diff line
@@ -620,32 +620,17 @@ static struct files_struct *alloc_files(void) 
	return newf;

}



static int copy_files(unsigned long clone_flags, struct task_struct * tsk)

/*

 * Allocate a new files structure and copy contents from the

 * passed in files structure.

 */

static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)

{

	struct files_struct *oldf, *newf;

	struct files_struct *newf;

	struct file **old_fds, **new_fds;

	int open_files, size, i, error = 0, expand;

	int open_files, size, i, expand;

	struct fdtable *old_fdt, *new_fdt;



	/*

	 * A background process may not have any files ...

	 */

	oldf = current->files;

	if (!oldf)

		goto out;



	if (clone_flags & CLONE_FILES) {

		atomic_inc(&oldf->count);

		goto out;

	}



	/*

	 * Note: we may be using current for both targets (See exec.c)

	 * This works because we cache current->files (old) as oldf. Don't

	 * break this.

	 */

	tsk->files = NULL;

	error = -ENOMEM;

	newf = alloc_files();

	if (!newf)

		goto out;
@@ -674,9 +659,9 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 
	if (expand) {

		spin_unlock(&oldf->file_lock);

		spin_lock(&newf->file_lock);

		error = expand_files(newf, open_files-1);

		*errorp = expand_files(newf, open_files-1);

		spin_unlock(&newf->file_lock);

		if (error < 0)

		if (*errorp < 0)

			goto out_release;

		new_fdt = files_fdtable(newf);

		/*
@@ -725,10 +710,8 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 
		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);

	}



	tsk->files = newf;

	error = 0;

out:

	return error;

	return newf;



out_release:

	free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
@@ -738,6 +721,40 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 
	goto out;

}



static int copy_files(unsigned long clone_flags, struct task_struct * tsk)

{

	struct files_struct *oldf, *newf;

	int error = 0;



	/*

	 * A background process may not have any files ...

	 */

	oldf = current->files;

	if (!oldf)

		goto out;



	if (clone_flags & CLONE_FILES) {

		atomic_inc(&oldf->count);

		goto out;

	}



	/*

	 * Note: we may be using current for both targets (See exec.c)

	 * This works because we cache current->files (old) as oldf. Don't

	 * break this.

	 */

	tsk->files = NULL;

	error = -ENOMEM;

	newf = dup_fd(oldf, &error);

	if (!newf)

		goto out;



	tsk->files = newf;

	error = 0;

out:

	return error;

}



/*

 *	Helper to unshare the files of the current task.

 *	We don't want to expose copy_files internals to
@@ -1463,15 +1480,19 @@ static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 
}



/*

 * Unsharing of files for tasks created with CLONE_FILES is not supported yet

 * Unshare file descriptor table if it is being shared

 */

static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)

{

	struct files_struct *fd = current->files;

	int error = 0;



	if ((unshare_flags & CLONE_FILES) &&

	    (fd && atomic_read(&fd->count) > 1))

		return -EINVAL;

	    (fd && atomic_read(&fd->count) > 1)) {

		*new_fdp = dup_fd(fd, &error);

		if (!*new_fdp)

			return error;

	}



	return 0;

}