fs/readdir.c - third_party/kernel - Git at Google

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

 #include <linux/stddef.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/time.h>
 #include <linux/mm.h>
 #include <linux/errno.h>
 #include <linux/stat.h>
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/fsnotify.h>
 #include <linux/dirent.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/unistd.h>
 #include <linux/compat.h>
 #include <linux/uaccess.h>

 #include <asm/unaligned.h>

 /*
  * Note the "unsafe_put_user() semantics: we goto a
  * label for errors.
  */
 #define unsafe_copy_dirent_name(_dst, _src, _len, label) do {	\
 	char __user *dst = (_dst);				\
 	const char *src = (_src);				\
 	size_t len = (_len);					\
 	unsafe_put_user(0, dst+len, label);			\
 	unsafe_copy_to_user(dst, src, len, label);		\
 } while (0)


 int iterate_dir(struct file *file, struct dir_context *ctx)
 {
 	struct inode *inode = file_inode(file);
 	bool shared = false;
 	int res = -ENOTDIR;
 	if (file->f_op->iterate_shared)
 		shared = true;
 	else if (!file->f_op->iterate)
 		goto out;

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

 	if (shared)
 		res = down_read_killable(&inode->i_rwsem);
 	else
 		res = down_write_killable(&inode->i_rwsem);
 	if (res)
 		goto out;

 	res = -ENOENT;
 	if (!IS_DEADDIR(inode)) {
 		ctx->pos = file->f_pos;
 		if (shared)
 			res = file->f_op->iterate_shared(file, ctx);
 		else
 			res = file->f_op->iterate(file, ctx);
 		file->f_pos = ctx->pos;
 		fsnotify_access(file);
 		file_accessed(file);
 	}
 	if (shared)
 		inode_unlock_shared(inode);
 	else
 		inode_unlock(inode);
 out:
 	return res;
 }
 EXPORT_SYMBOL(iterate_dir);

 /*
  * POSIX says that a dirent name cannot contain NULL or a '/'.
  *
  * It's not 100% clear what we should really do in this case.
  * The filesystem is clearly corrupted, but returning a hard
  * error means that you now don't see any of the other names
  * either, so that isn't a perfect alternative.
  *
  * And if you return an error, what error do you use? Several
  * filesystems seem to have decided on EUCLEAN being the error
  * code for EFSCORRUPTED, and that may be the error to use. Or
  * just EIO, which is perhaps more obvious to users.
  *
  * In order to see the other file names in the directory, the
  * caller might want to make this a "soft" error: skip the
  * entry, and return the error at the end instead.
  *
  * Note that this should likely do a "memchr(name, 0, len)"
  * check too, since that would be filesystem corruption as
  * well. However, that case can't actually confuse user space,
  * which has to do a strlen() on the name anyway to find the
  * filename length, and the above "soft error" worry means
  * that it's probably better left alone until we have that
  * issue clarified.
  *
  * Note the PATH_MAX check - it's arbitrary but the real
  * kernel limit on a possible path component, not NAME_MAX,
  * which is the technical standard limit.
  */
 static int verify_dirent_name(const char *name, int len)
 {
 	if (len <= 0 || len >= PATH_MAX)
 		return -EIO;
 	if (memchr(name, '/', len))
 		return -EIO;
 	return 0;
 }

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

 static bool fillonedir(struct dir_context *ctx, const char *name, int namlen,
 		      loff_t offset, u64 ino, unsigned int d_type)
 {
 	struct readdir_callback *buf =
 		container_of(ctx, struct readdir_callback, ctx);
 	struct old_linux_dirent __user * dirent;
 	unsigned long d_ino;

 	if (buf->result)
 		return false;
 	buf->result = verify_dirent_name(name, namlen);
 	if (buf->result)
 		return false;
 	d_ino = ino;
 	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 		buf->result = -EOVERFLOW;
 		return false;
 	}
 	buf->result++;
 	dirent = buf->dirent;
 	if (!user_write_access_begin(dirent,
 			(unsigned long)(dirent->d_name + namlen + 1) -
 				(unsigned long)dirent))
 		goto efault;
 	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
 	unsafe_put_user(offset, &dirent->d_offset, efault_end);
 	unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
 	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
 	user_write_access_end();
 	return true;
 efault_end:
 	user_write_access_end();
 efault:
 	buf->result = -EFAULT;
 	return false;
 }

 SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
 		struct old_linux_dirent __user *, dirent, unsigned int, count)
 {
 	int error;
 	struct fd f = fdget_pos(fd);
 	struct readdir_callback buf = {
 		.ctx.actor = 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;
 }

 #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 {
 	struct dir_context ctx;
 	struct linux_dirent __user * current_dir;
 	int prev_reclen;
 	int count;
 	int error;
 };

 static bool filldir(struct dir_context *ctx, const char *name, int namlen,
 		   loff_t offset, u64 ino, unsigned int d_type)
 {
 	struct linux_dirent __user *dirent, *prev;
 	struct getdents_callback *buf =
 		container_of(ctx, struct getdents_callback, ctx);
 	unsigned long d_ino;
 	int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
 		sizeof(long));
 	int prev_reclen;

 	buf->error = verify_dirent_name(name, namlen);
 	if (unlikely(buf->error))
 		return false;
 	buf->error = -EINVAL;	/* only used if we fail.. */
 	if (reclen > buf->count)
 		return false;
 	d_ino = ino;
 	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 		buf->error = -EOVERFLOW;
 		return false;
 	}
 	prev_reclen = buf->prev_reclen;
 	if (prev_reclen && signal_pending(current))
 		return false;
 	dirent = buf->current_dir;
 	prev = (void __user *) dirent - prev_reclen;
 	if (!user_write_access_begin(prev, reclen + prev_reclen))
 		goto efault;

 	/* This might be 'dirent->d_off', but if so it will get overwritten */
 	unsafe_put_user(offset, &prev->d_off, efault_end);
 	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
 	unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
 	unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
 	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
 	user_write_access_end();

 	buf->current_dir = (void __user *)dirent + reclen;
 	buf->prev_reclen = reclen;
 	buf->count -= reclen;
 	return true;
 efault_end:
 	user_write_access_end();
 efault:
 	buf->error = -EFAULT;
 	return false;
 }

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

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

 	error = iterate_dir(f.file, &buf.ctx);
 	if (error >= 0)
 		error = buf.error;
 	if (buf.prev_reclen) {
 		struct linux_dirent __user * lastdirent;
 		lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;

 		if (put_user(buf.ctx.pos, &lastdirent->d_off))
 			error = -EFAULT;
 		else
 			error = count - buf.count;
 	}
 	fdput_pos(f);
 	return error;
 }

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

 static bool filldir64(struct dir_context *ctx, const char *name, int namlen,
 		     loff_t offset, u64 ino, unsigned int d_type)
 {
 	struct linux_dirent64 __user *dirent, *prev;
 	struct getdents_callback64 *buf =
 		container_of(ctx, struct getdents_callback64, ctx);
 	int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 		sizeof(u64));
 	int prev_reclen;

 	buf->error = verify_dirent_name(name, namlen);
 	if (unlikely(buf->error))
 		return false;
 	buf->error = -EINVAL;	/* only used if we fail.. */
 	if (reclen > buf->count)
 		return false;
 	prev_reclen = buf->prev_reclen;
 	if (prev_reclen && signal_pending(current))
 		return false;
 	dirent = buf->current_dir;
 	prev = (void __user *)dirent - prev_reclen;
 	if (!user_write_access_begin(prev, reclen + prev_reclen))
 		goto efault;

 	/* This might be 'dirent->d_off', but if so it will get overwritten */
 	unsafe_put_user(offset, &prev->d_off, efault_end);
 	unsafe_put_user(ino, &dirent->d_ino, efault_end);
 	unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
 	unsafe_put_user(d_type, &dirent->d_type, efault_end);
 	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
 	user_write_access_end();

 	buf->prev_reclen = reclen;
 	buf->current_dir = (void __user *)dirent + reclen;
 	buf->count -= reclen;
 	return true;

 efault_end:
 	user_write_access_end();
 efault:
 	buf->error = -EFAULT;
 	return false;
 }

 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 		struct linux_dirent64 __user *, dirent, unsigned int, count)
 {
 	struct fd f;
 	struct getdents_callback64 buf = {
 		.ctx.actor = filldir64,
 		.count = count,
 		.current_dir = dirent
 	};
 	int error;

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

 	error = iterate_dir(f.file, &buf.ctx);
 	if (error >= 0)
 		error = buf.error;
 	if (buf.prev_reclen) {
 		struct linux_dirent64 __user * lastdirent;
 		typeof(lastdirent->d_off) d_off = buf.ctx.pos;

 		lastdirent = (void __user *) buf.current_dir - buf.prev_reclen;
 		if (put_user(d_off, &lastdirent->d_off))
 			error = -EFAULT;
 		else
 			error = count - buf.count;
 	}
 	fdput_pos(f);
 	return error;
 }

 #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 bool 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 false;
 	buf->result = verify_dirent_name(name, namlen);
 	if (buf->result)
 		return false;
 	d_ino = ino;
 	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 		buf->result = -EOVERFLOW;
 		return false;
 	}
 	buf->result++;
 	dirent = buf->dirent;
 	if (!user_write_access_begin(dirent,
 			(unsigned long)(dirent->d_name + namlen + 1) -
 				(unsigned long)dirent))
 		goto efault;
 	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
 	unsafe_put_user(offset, &dirent->d_offset, efault_end);
 	unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
 	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
 	user_write_access_end();
 	return true;
 efault_end:
 	user_write_access_end();
 efault:
 	buf->result = -EFAULT;
 	return false;
 }

 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;
 	int prev_reclen;
 	int count;
 	int error;
 };

 static bool 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, *prev;
 	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));
 	int prev_reclen;

 	buf->error = verify_dirent_name(name, namlen);
 	if (unlikely(buf->error))
 		return false;
 	buf->error = -EINVAL;	/* only used if we fail.. */
 	if (reclen > buf->count)
 		return false;
 	d_ino = ino;
 	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 		buf->error = -EOVERFLOW;
 		return false;
 	}
 	prev_reclen = buf->prev_reclen;
 	if (prev_reclen && signal_pending(current))
 		return false;
 	dirent = buf->current_dir;
 	prev = (void __user *) dirent - prev_reclen;
 	if (!user_write_access_begin(prev, reclen + prev_reclen))
 		goto efault;

 	unsafe_put_user(offset, &prev->d_off, efault_end);
 	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
 	unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
 	unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
 	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
 	user_write_access_end();

 	buf->prev_reclen = reclen;
 	buf->current_dir = (void __user *)dirent + reclen;
 	buf->count -= reclen;
 	return true;
 efault_end:
 	user_write_access_end();
 efault:
 	buf->error = -EFAULT;
 	return false;
 }

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

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

 	error = iterate_dir(f.file, &buf.ctx);
 	if (error >= 0)
 		error = buf.error;
 	if (buf.prev_reclen) {
 		struct compat_linux_dirent __user * lastdirent;
 		lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;

 		if (put_user(buf.ctx.pos, &lastdirent->d_off))
 			error = -EFAULT;
 		else
 			error = count - buf.count;
 	}
 	fdput_pos(f);
 	return error;
 }
 #endif
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/fs/readdir.c
	*
	* Copyright (C) 1995 Linus Torvalds
	*/

	#include <linux/stddef.h>
	#include <linux/kernel.h>
	#include <linux/export.h>
	#include <linux/time.h>
	#include <linux/mm.h>
	#include <linux/errno.h>
	#include <linux/stat.h>
	#include <linux/file.h>
	#include <linux/fs.h>
	#include <linux/fsnotify.h>
	#include <linux/dirent.h>
	#include <linux/security.h>
	#include <linux/syscalls.h>
	#include <linux/unistd.h>
	#include <linux/compat.h>
	#include <linux/uaccess.h>

	#include <asm/unaligned.h>

	/*
	* Note the "unsafe_put_user() semantics: we goto a
	* label for errors.
	*/
	#define unsafe_copy_dirent_name(_dst, _src, _len, label) do { \
	char __user *dst = (_dst); \
	const char *src = (_src); \
	size_t len = (_len); \
	unsafe_put_user(0, dst+len, label); \
	unsafe_copy_to_user(dst, src, len, label); \
	} while (0)


	int iterate_dir(struct file file, struct dir_context ctx)
	{
	struct inode *inode = file_inode(file);
	bool shared = false;
	int res = -ENOTDIR;
	if (file->f_op->iterate_shared)
	shared = true;
	else if (!file->f_op->iterate)
	goto out;

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

	if (shared)
	res = down_read_killable(&inode->i_rwsem);
	else
	res = down_write_killable(&inode->i_rwsem);
	if (res)
	goto out;

	res = -ENOENT;
	if (!IS_DEADDIR(inode)) {
	ctx->pos = file->f_pos;
	if (shared)
	res = file->f_op->iterate_shared(file, ctx);
	else
	res = file->f_op->iterate(file, ctx);
	file->f_pos = ctx->pos;
	fsnotify_access(file);
	file_accessed(file);
	}
	if (shared)
	inode_unlock_shared(inode);
	else
	inode_unlock(inode);
	out:
	return res;
	}
	EXPORT_SYMBOL(iterate_dir);

	/*
	* POSIX says that a dirent name cannot contain NULL or a '/'.
	*
	* It's not 100% clear what we should really do in this case.
	* The filesystem is clearly corrupted, but returning a hard
	* error means that you now don't see any of the other names
	* either, so that isn't a perfect alternative.
	*
	* And if you return an error, what error do you use? Several
	* filesystems seem to have decided on EUCLEAN being the error
	* code for EFSCORRUPTED, and that may be the error to use. Or
	* just EIO, which is perhaps more obvious to users.
	*
	* In order to see the other file names in the directory, the
	* caller might want to make this a "soft" error: skip the
	* entry, and return the error at the end instead.
	*
	* Note that this should likely do a "memchr(name, 0, len)"
	* check too, since that would be filesystem corruption as
	* well. However, that case can't actually confuse user space,
	* which has to do a strlen() on the name anyway to find the
	* filename length, and the above "soft error" worry means
	* that it's probably better left alone until we have that
	* issue clarified.
	*
	* Note the PATH_MAX check - it's arbitrary but the real
	* kernel limit on a possible path component, not NAME_MAX,
	* which is the technical standard limit.
	*/
	static int verify_dirent_name(const char *name, int len)
	{
	if (len <= 0 \|\| len >= PATH_MAX)
	return -EIO;
	if (memchr(name, '/', len))
	return -EIO;
	return 0;
	}

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

	static bool fillonedir(struct dir_context ctx, const char name, int namlen,
	loff_t offset, u64 ino, unsigned int d_type)
	{
	struct readdir_callback *buf =
	container_of(ctx, struct readdir_callback, ctx);
	struct old_linux_dirent __user * dirent;
	unsigned long d_ino;

	if (buf->result)
	return false;
	buf->result = verify_dirent_name(name, namlen);
	if (buf->result)
	return false;
	d_ino = ino;
	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
	buf->result = -EOVERFLOW;
	return false;
	}
	buf->result++;
	dirent = buf->dirent;
	if (!user_write_access_begin(dirent,
	(unsigned long)(dirent->d_name + namlen + 1) -
	(unsigned long)dirent))
	goto efault;
	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
	unsafe_put_user(offset, &dirent->d_offset, efault_end);
	unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
	user_write_access_end();
	return true;
	efault_end:
	user_write_access_end();
	efault:
	buf->result = -EFAULT;
	return false;
	}

	SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
	struct old_linux_dirent __user *, dirent, unsigned int, count)
	{
	int error;
	struct fd f = fdget_pos(fd);
	struct readdir_callback buf = {
	.ctx.actor = 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;
	}

	#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 {
	struct dir_context ctx;
	struct linux_dirent __user * current_dir;
	int prev_reclen;
	int count;
	int error;
	};

	static bool filldir(struct dir_context ctx, const char name, int namlen,
	loff_t offset, u64 ino, unsigned int d_type)
	{
	struct linux_dirent __user dirent, prev;
	struct getdents_callback *buf =
	container_of(ctx, struct getdents_callback, ctx);
	unsigned long d_ino;
	int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
	sizeof(long));
	int prev_reclen;

	buf->error = verify_dirent_name(name, namlen);
	if (unlikely(buf->error))
	return false;
	buf->error = -EINVAL; /* only used if we fail.. */
	if (reclen > buf->count)
	return false;
	d_ino = ino;
	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
	buf->error = -EOVERFLOW;
	return false;
	}
	prev_reclen = buf->prev_reclen;
	if (prev_reclen && signal_pending(current))
	return false;
	dirent = buf->current_dir;
	prev = (void __user *) dirent - prev_reclen;
	if (!user_write_access_begin(prev, reclen + prev_reclen))
	goto efault;

	/* This might be 'dirent->d_off', but if so it will get overwritten */
	unsafe_put_user(offset, &prev->d_off, efault_end);
	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
	unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
	unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
	user_write_access_end();

	buf->current_dir = (void __user *)dirent + reclen;
	buf->prev_reclen = reclen;
	buf->count -= reclen;
	return true;
	efault_end:
	user_write_access_end();
	efault:
	buf->error = -EFAULT;
	return false;
	}

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

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

	error = iterate_dir(f.file, &buf.ctx);
	if (error >= 0)
	error = buf.error;
	if (buf.prev_reclen) {
	struct linux_dirent __user * lastdirent;
	lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;

	if (put_user(buf.ctx.pos, &lastdirent->d_off))
	error = -EFAULT;
	else
	error = count - buf.count;
	}
	fdput_pos(f);
	return error;
	}

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

	static bool filldir64(struct dir_context ctx, const char name, int namlen,
	loff_t offset, u64 ino, unsigned int d_type)
	{
	struct linux_dirent64 __user dirent, prev;
	struct getdents_callback64 *buf =
	container_of(ctx, struct getdents_callback64, ctx);
	int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
	sizeof(u64));
	int prev_reclen;

	buf->error = verify_dirent_name(name, namlen);
	if (unlikely(buf->error))
	return false;
	buf->error = -EINVAL; /* only used if we fail.. */
	if (reclen > buf->count)
	return false;
	prev_reclen = buf->prev_reclen;
	if (prev_reclen && signal_pending(current))
	return false;
	dirent = buf->current_dir;
	prev = (void __user *)dirent - prev_reclen;
	if (!user_write_access_begin(prev, reclen + prev_reclen))
	goto efault;

	/* This might be 'dirent->d_off', but if so it will get overwritten */
	unsafe_put_user(offset, &prev->d_off, efault_end);
	unsafe_put_user(ino, &dirent->d_ino, efault_end);
	unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
	unsafe_put_user(d_type, &dirent->d_type, efault_end);
	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
	user_write_access_end();

	buf->prev_reclen = reclen;
	buf->current_dir = (void __user *)dirent + reclen;
	buf->count -= reclen;
	return true;

	efault_end:
	user_write_access_end();
	efault:
	buf->error = -EFAULT;
	return false;
	}

	SYSCALL_DEFINE3(getdents64, unsigned int, fd,
	struct linux_dirent64 __user *, dirent, unsigned int, count)
	{
	struct fd f;
	struct getdents_callback64 buf = {
	.ctx.actor = filldir64,
	.count = count,
	.current_dir = dirent
	};
	int error;

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

	error = iterate_dir(f.file, &buf.ctx);
	if (error >= 0)
	error = buf.error;
	if (buf.prev_reclen) {
	struct linux_dirent64 __user * lastdirent;
	typeof(lastdirent->d_off) d_off = buf.ctx.pos;

	lastdirent = (void __user *) buf.current_dir - buf.prev_reclen;
	if (put_user(d_off, &lastdirent->d_off))
	error = -EFAULT;
	else
	error = count - buf.count;
	}
	fdput_pos(f);
	return error;
	}

	#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 bool 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 false;
	buf->result = verify_dirent_name(name, namlen);
	if (buf->result)
	return false;
	d_ino = ino;
	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
	buf->result = -EOVERFLOW;
	return false;
	}
	buf->result++;
	dirent = buf->dirent;
	if (!user_write_access_begin(dirent,
	(unsigned long)(dirent->d_name + namlen + 1) -
	(unsigned long)dirent))
	goto efault;
	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
	unsafe_put_user(offset, &dirent->d_offset, efault_end);
	unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
	user_write_access_end();
	return true;
	efault_end:
	user_write_access_end();
	efault:
	buf->result = -EFAULT;
	return false;
	}

	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;
	int prev_reclen;
	int count;
	int error;
	};

	static bool 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, prev;
	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));
	int prev_reclen;

	buf->error = verify_dirent_name(name, namlen);
	if (unlikely(buf->error))
	return false;
	buf->error = -EINVAL; /* only used if we fail.. */
	if (reclen > buf->count)
	return false;
	d_ino = ino;
	if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
	buf->error = -EOVERFLOW;
	return false;
	}
	prev_reclen = buf->prev_reclen;
	if (prev_reclen && signal_pending(current))
	return false;
	dirent = buf->current_dir;
	prev = (void __user *) dirent - prev_reclen;
	if (!user_write_access_begin(prev, reclen + prev_reclen))
	goto efault;

	unsafe_put_user(offset, &prev->d_off, efault_end);
	unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
	unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
	unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
	unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
	user_write_access_end();

	buf->prev_reclen = reclen;
	buf->current_dir = (void __user *)dirent + reclen;
	buf->count -= reclen;
	return true;
	efault_end:
	user_write_access_end();
	efault:
	buf->error = -EFAULT;
	return false;
	}

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

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

	error = iterate_dir(f.file, &buf.ctx);
	if (error >= 0)
	error = buf.error;
	if (buf.prev_reclen) {
	struct compat_linux_dirent __user * lastdirent;
	lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;

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