path: root/fs/fcntl.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/fcntl.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/syscalls.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/sched/task.h>
#include <linux/fs.h>
#include <linux/filelock.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/capability.h>
#include <linux/dnotify.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/pipe_fs_i.h>
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/signal.h>
#include <linux/rcupdate.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/memfd.h>
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/rw_hint.h>

#include <linux/poll.h>
#include <asm/siginfo.h>
#include <linux/uaccess.h>

#include "internal.h"

#define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)

static int setfl(int fd, struct file * filp, unsigned int arg)
{
	struct inode * inode = file_inode(filp);
	int error = 0;

	/*
	 * O_APPEND cannot be cleared if the file is marked as append-only
	 * and the file is open for write.
	 */
	if (((arg ^ filp->f_flags) & O_APPEND) && IS_APPEND(inode))
		return -EPERM;

	/* O_NOATIME can only be set by the owner or superuser */
	if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
		if (!inode_owner_or_capable(file_mnt_idmap(filp), inode))
			return -EPERM;

	/* required for strict SunOS emulation */
	if (O_NONBLOCK != O_NDELAY)
	       if (arg & O_NDELAY)
		   arg |= O_NONBLOCK;

	/* Pipe packetized mode is controlled by O_DIRECT flag */
	if (!S_ISFIFO(inode->i_mode) &&
	    (arg & O_DIRECT) &&
	    !(filp->f_mode & FMODE_CAN_ODIRECT))
		return -EINVAL;

	if (filp->f_op->check_flags)
		error = filp->f_op->check_flags(arg);
	if (error)
		return error;

	/*
	 * ->fasync() is responsible for setting the FASYNC bit.
	 */
	if (((arg ^ filp->f_flags) & FASYNC) && filp->f_op->fasync) {
		error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
		if (error < 0)
			goto out;
		if (error > 0)
			error = 0;
	}
	spin_lock(&filp->f_lock);
	filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
	filp->f_iocb_flags = iocb_flags(filp);
	spin_unlock(&filp->f_lock);

 out:
	return error;
}

/*
 * Allocate an file->f_owner struct if it doesn't exist, handling racing
 * allocations correctly.
 */
int file_f_owner_allocate(struct file *file)
{
	struct fown_struct *f_owner;

	f_owner = file_f_owner(file);
	if (f_owner)
		return 0;

	f_owner = kzalloc(sizeof(struct fown_struct), GFP_KERNEL);
	if (!f_owner)
		return -ENOMEM;

	rwlock_init(&f_owner->lock);
	f_owner->file = file;
	/* If someone else raced us, drop our allocation. */
	if (unlikely(cmpxchg(&file->f_owner, NULL, f_owner)))
		kfree(f_owner);
	return 0;
}
EXPORT_SYMBOL(file_f_owner_allocate);

void file_f_owner_release(struct file *file)
{
	struct fown_struct *f_owner;

	f_owner = file_f_owner(file);
	if (f_owner) {
		put_pid(f_owner->pid);
		kfree(f_owner);
	}
}

void __f_setown(struct file *filp, struct pid *pid, enum pid_type type,
		int force)
{
	struct fown_struct *f_owner;

	f_owner = file_f_owner(filp);
	if (WARN_ON_ONCE(!f_owner))
		return;

	write_lock_irq(&f_owner->lock);
	if (force || !f_owner->pid) {
		put_pid(f_owner-><