readdir.c 11.4 KB
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// SPDX-License-Identifier: GPL-2.0
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/*
 *  linux/fs/readdir.c
 *
 *  Copyright (C) 1995  Linus Torvalds
 */

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#include <linux/stddef.h>
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/time.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/file.h>
#include <linux/fs.h>
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#include <linux/fsnotify.h>
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#include <linux/dirent.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
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#include <linux/compat.h>
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#include <linux/uaccess.h>
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int iterate_dir(struct file *file, struct dir_context *ctx)
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{
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	struct inode *inode = file_inode(file);
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	bool shared = false;
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	int res = -ENOTDIR;
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	if (file->f_op->iterate_shared)
		shared = true;
	else if (!file->f_op->iterate)
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		goto out;

	res = security_file_permission(file, MAY_READ);
	if (res)
		goto out;

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	if (shared)
		res = down_read_killable(&inode->i_rwsem);
	else
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		res = down_write_killable(&inode->i_rwsem);
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	if (res)
		goto out;
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	res = -ENOENT;
	if (!IS_DEADDIR(inode)) {
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		ctx->pos = file->f_pos;
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		if (shared)
			res = file->f_op->iterate_shared(file, ctx);
		else
			res = file->f_op->iterate(file, ctx);
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		file->f_pos = ctx->pos;
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		fsnotify_access(file);
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		file_accessed(file);
	}
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	if (shared)
		inode_unlock_shared(inode);
	else
		inode_unlock(inode);
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out:
	return res;
}
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EXPORT_SYMBOL(iterate_dir);
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/*
 * Traditional linux readdir() handling..
 *
 * "count=1" is a special case, meaning that the buffer is one
 * dirent-structure in size and that the code can't handle more
 * anyway. Thus the special "fillonedir()" function for that
 * case (the low-level handlers don't need to care about this).
 */

#ifdef __ARCH_WANT_OLD_READDIR

struct old_linux_dirent {
	unsigned long	d_ino;
	unsigned long	d_offset;
	unsigned short	d_namlen;
	char		d_name[1];
};

struct readdir_callback {
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	struct dir_context ctx;
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	struct old_linux_dirent __user * dirent;
	int result;
};

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static int fillonedir(struct dir_context *ctx, const char *name, int namlen,
		      loff_t offset, u64 ino, unsigned int d_type)
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{
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	struct readdir_callback *buf =
		container_of(ctx, struct readdir_callback, ctx);
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	struct old_linux_dirent __user * dirent;
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	unsigned long d_ino;
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	if (buf->result)
		return -EINVAL;
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	d_ino = ino;
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	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
		buf->result = -EOVERFLOW;
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		return -EOVERFLOW;
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	}
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	buf->result++;
	dirent = buf->dirent;
	if (!access_ok(VERIFY_WRITE, dirent,
			(unsigned long)(dirent->d_name + namlen + 1) -
				(unsigned long)dirent))
		goto efault;
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	if (	__put_user(d_ino, &dirent->d_ino) ||
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		__put_user(offset, &dirent->d_offset) ||
		__put_user(namlen, &dirent->d_namlen) ||
		__copy_to_user(dirent->d_name, name, namlen) ||
		__put_user(0, dirent->d_name + namlen))
		goto efault;
	return 0;
efault:
	buf->result = -EFAULT;
	return -EFAULT;
}

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SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
		struct old_linux_dirent __user *, dirent, unsigned int, count)
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{
	int error;
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	struct fd f = fdget_pos(fd);
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	struct readdir_callback buf = {
		.ctx.actor = fillonedir,
		.dirent = dirent
	};
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	if (!f.file)
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		return -EBADF;
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	error = iterate_dir(f.file, &buf.ctx);
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	if (buf.result)
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		error = buf.result;

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	fdput_pos(f);
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	return error;
}

#endif /* __ARCH_WANT_OLD_READDIR */

/*
 * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 * interface. 
 */
struct linux_dirent {
	unsigned long	d_ino;
	unsigned long	d_off;
	unsigned short	d_reclen;
	char		d_name[1];
};

struct getdents_callback {
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	struct dir_context ctx;
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	struct linux_dirent __user * current_dir;
	struct linux_dirent __user * previous;
	int count;
	int error;
};

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static int filldir(struct dir_context *ctx, const char *name, int namlen,
		   loff_t offset, u64 ino, unsigned int d_type)
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{
	struct linux_dirent __user * dirent;
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	struct getdents_callback *buf =
		container_of(ctx, struct getdents_callback, ctx);
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	unsigned long d_ino;
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	int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
		sizeof(long));
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	buf->error = -EINVAL;	/* only used if we fail.. */
	if (reclen > buf->count)
		return -EINVAL;
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	d_ino = ino;
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	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
		buf->error = -EOVERFLOW;
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		return -EOVERFLOW;
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	}
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	dirent = buf->previous;
	if (dirent) {
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		if (signal_pending(current))
			return -EINTR;
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		if (__put_user(offset, &dirent->d_off))
			goto efault;
	}
	dirent = buf->current_dir;
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	if (__put_user(d_ino, &dirent->d_ino))
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		goto efault;
	if (__put_user(reclen, &dirent->d_reclen))
		goto efault;
	if (copy_to_user(dirent->d_name, name, namlen))
		goto efault;
	if (__put_user(0, dirent->d_name + namlen))
		goto efault;
	if (__put_user(d_type, (char __user *) dirent + reclen - 1))
		goto efault;
	buf->previous = dirent;
	dirent = (void __user *)dirent + reclen;
	buf->current_dir = dirent;
	buf->count -= reclen;
	return 0;
efault:
	buf->error = -EFAULT;
	return -EFAULT;
}

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SYSCALL_DEFINE3(getdents, unsigned int, fd,
		struct linux_dirent __user *, dirent, unsigned int, count)
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{
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	struct fd f;
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	struct linux_dirent __user * lastdirent;
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	struct getdents_callback buf = {
		.ctx.actor = filldir,
		.count = count,
		.current_dir = dirent
	};
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	int error;

	if (!access_ok(VERIFY_WRITE, dirent, count))
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		return -EFAULT;
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	f = fdget_pos(fd);
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	if (!f.file)
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		return -EBADF;
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	error = iterate_dir(f.file, &buf.ctx);
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	if (error >= 0)
		error = buf.error;
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	lastdirent = buf.previous;
	if (lastdirent) {
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		if (put_user(buf.ctx.pos, &lastdirent->d_off))
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			error = -EFAULT;
		else
			error = count - buf.count;
	}
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	fdput_pos(f);
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	return error;
}

struct getdents_callback64 {
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	struct dir_context ctx;
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	struct linux_dirent64 __user * current_dir;
	struct linux_dirent64 __user * previous;
	int count;
	int error;
};

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static int filldir64(struct dir_context *ctx, const char *name, int namlen,
		     loff_t offset, u64 ino, unsigned int d_type)
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{
	struct linux_dirent64 __user *dirent;
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	struct getdents_callback64 *buf =
		container_of(ctx, struct getdents_callback64, ctx);
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	int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
		sizeof(u64));
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	buf->error = -EINVAL;	/* only used if we fail.. */
	if (reclen > buf->count)
		return -EINVAL;
	dirent = buf->previous;
	if (dirent) {
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		if (signal_pending(current))
			return -EINTR;
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		if (__put_user(offset, &dirent->d_off))
			goto efault;
	}
	dirent = buf->current_dir;
	if (__put_user(ino, &dirent->d_ino))
		goto efault;
	if (__put_user(0, &dirent->d_off))
		goto efault;
	if (__put_user(reclen, &dirent->d_reclen))
		goto efault;
	if (__put_user(d_type, &dirent->d_type))
		goto efault;
	if (copy_to_user(dirent->d_name, name, namlen))
		goto efault;
	if (__put_user(0, dirent->d_name + namlen))
		goto efault;
	buf->previous = dirent;
	dirent = (void __user *)dirent + reclen;
	buf->current_dir = dirent;
	buf->count -= reclen;
	return 0;
efault:
	buf->error = -EFAULT;
	return -EFAULT;
}

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int ksys_getdents64(unsigned int fd, struct linux_dirent64 __user *dirent,
		    unsigned int count)
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{
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	struct fd f;
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	struct linux_dirent64 __user * lastdirent;
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	struct getdents_callback64 buf = {
		.ctx.actor = filldir64,
		.count = count,
		.current_dir = dirent
	};
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	int error;

	if (!access_ok(VERIFY_WRITE, dirent, count))
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		return -EFAULT;
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	f = fdget_pos(fd);
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	if (!f.file)
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		return -EBADF;
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	error = iterate_dir(f.file, &buf.ctx);
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	if (error >= 0)
		error = buf.error;
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	lastdirent = buf.previous;
	if (lastdirent) {
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		typeof(lastdirent->d_off) d_off = buf.ctx.pos;
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		if (__put_user(d_off, &lastdirent->d_off))
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			error = -EFAULT;
		else
			error = count - buf.count;
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	}
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	fdput_pos(f);
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	return error;
}
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SYSCALL_DEFINE3(getdents64, unsigned int, fd,
		struct linux_dirent64 __user *, dirent, unsigned int, count)
{
	return ksys_getdents64(fd, dirent, count);
}

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#ifdef CONFIG_COMPAT
struct compat_old_linux_dirent {
	compat_ulong_t	d_ino;
	compat_ulong_t	d_offset;
	unsigned short	d_namlen;
	char		d_name[1];
};

struct compat_readdir_callback {
	struct dir_context ctx;
	struct compat_old_linux_dirent __user *dirent;
	int result;
};

static int compat_fillonedir(struct dir_context *ctx, const char *name,
			     int namlen, loff_t offset, u64 ino,
			     unsigned int d_type)
{
	struct compat_readdir_callback *buf =
		container_of(ctx, struct compat_readdir_callback, ctx);
	struct compat_old_linux_dirent __user *dirent;
	compat_ulong_t d_ino;

	if (buf->result)
		return -EINVAL;
	d_ino = ino;
	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
		buf->result = -EOVERFLOW;
		return -EOVERFLOW;
	}
	buf->result++;
	dirent = buf->dirent;
	if (!access_ok(VERIFY_WRITE, dirent,
			(unsigned long)(dirent->d_name + namlen + 1) -
				(unsigned long)dirent))
		goto efault;
	if (	__put_user(d_ino, &dirent->d_ino) ||
		__put_user(offset, &dirent->d_offset) ||
		__put_user(namlen, &dirent->d_namlen) ||
		__copy_to_user(dirent->d_name, name, namlen) ||
		__put_user(0, dirent->d_name + namlen))
		goto efault;
	return 0;
efault:
	buf->result = -EFAULT;
	return -EFAULT;
}

COMPAT_SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
		struct compat_old_linux_dirent __user *, dirent, unsigned int, count)
{
	int error;
	struct fd f = fdget_pos(fd);
	struct compat_readdir_callback buf = {
		.ctx.actor = compat_fillonedir,
		.dirent = dirent
	};

	if (!f.file)
		return -EBADF;

	error = iterate_dir(f.file, &buf.ctx);
	if (buf.result)
		error = buf.result;

	fdput_pos(f);
	return error;
}

struct compat_linux_dirent {
	compat_ulong_t	d_ino;
	compat_ulong_t	d_off;
	unsigned short	d_reclen;
	char		d_name[1];
};

struct compat_getdents_callback {
	struct dir_context ctx;
	struct compat_linux_dirent __user *current_dir;
	struct compat_linux_dirent __user *previous;
	int count;
	int error;
};

static int compat_filldir(struct dir_context *ctx, const char *name, int namlen,
		loff_t offset, u64 ino, unsigned int d_type)
{
	struct compat_linux_dirent __user * dirent;
	struct compat_getdents_callback *buf =
		container_of(ctx, struct compat_getdents_callback, ctx);
	compat_ulong_t d_ino;
	int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +
		namlen + 2, sizeof(compat_long_t));

	buf->error = -EINVAL;	/* only used if we fail.. */
	if (reclen > buf->count)
		return -EINVAL;
	d_ino = ino;
	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
		buf->error = -EOVERFLOW;
		return -EOVERFLOW;
	}
	dirent = buf->previous;
	if (dirent) {
		if (signal_pending(current))
			return -EINTR;
		if (__put_user(offset, &dirent->d_off))
			goto efault;
	}
	dirent = buf->current_dir;
	if (__put_user(d_ino, &dirent->d_ino))
		goto efault;
	if (__put_user(reclen, &dirent->d_reclen))
		goto efault;
	if (copy_to_user(dirent->d_name, name, namlen))
		goto efault;
	if (__put_user(0, dirent->d_name + namlen))
		goto efault;
	if (__put_user(d_type, (char  __user *) dirent + reclen - 1))
		goto efault;
	buf->previous = dirent;
	dirent = (void __user *)dirent + reclen;
	buf->current_dir = dirent;
	buf->count -= reclen;
	return 0;
efault:
	buf->error = -EFAULT;
	return -EFAULT;
}

COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd,
		struct compat_linux_dirent __user *, dirent, unsigned int, count)
{
	struct fd f;
	struct compat_linux_dirent __user * lastdirent;
	struct compat_getdents_callback buf = {
		.ctx.actor = compat_filldir,
		.current_dir = dirent,
		.count = count
	};
	int error;

	if (!access_ok(VERIFY_WRITE, dirent, count))
		return -EFAULT;

	f = fdget_pos(fd);
	if (!f.file)
		return -EBADF;

	error = iterate_dir(f.file, &buf.ctx);
	if (error >= 0)
		error = buf.error;
	lastdirent = buf.previous;
	if (lastdirent) {
		if (put_user(buf.ctx.pos, &lastdirent->d_off))
			error = -EFAULT;
		else
			error = count - buf.count;
	}
	fdput_pos(f);
	return error;
}
#endif