// 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> #define dirent_size(dirent, len) offsetof(typeof(*(dirent)), d_name[len]) /* * Some filesystems were never converted to '->iterate_shared()' * and their directory iterators want the inode lock held for * writing. This wrapper allows for converting from the shared * semantics to the exclusive inode use. */int wrap_directory_iterator(struct file *file,			    struct dir_context *ctx,			    int (*iter)(struct file *, struct dir_context *)){	struct inode *inode = file_inode(file);	int ret; 	/*	 * We'd love to have an 'inode_upgrade_trylock()' operation,	 * see the comment in mmap_upgrade_trylock() in mm/memory.c.	 *	 * But considering this is for "filesystems that never got	 * converted", it really doesn't matter.	 *	 * Also note that since we have to return with the lock held	 * for reading, we can't use the "killable()" locking here,	 * since we do need to get the lock even if we're dying.	 *	 * We could do the write part killably and then get the read	 * lock unconditionally if it mattered, but see above on why	 * this does the very simplistic conversion.	 */	up_read(&inode->i_rwsem);	down_write(&inode->i_rwsem); 	/*	 * Since we dropped the inode lock, we should do the	 * DEADDIR test again. See 'iterate_dir()' below.	 *	 * Note that we don't need to re-do the f_pos games,	 * since the file must be locked wrt f_pos anyway.	 */	ret = -ENOENT;	if (!IS_DEADDIR(inode))		ret = iter(file, ctx); 	downgrade_write(&inode->i_rwsem);	return ret;}EXPORT_SYMBOL(wrap_directory_iterator); /* * 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);	int res = -ENOTDIR; 	if (!file->f_op->iterate_shared)		goto out; 	res = security_file_permission(file, MAY_READ);	if (res)		goto out; 	res = fsnotify_file_perm(file, MAY_READ);	if (res)		goto out; 	res = down_read_killable(&inode->i_rwsem);	if (res)		goto out; 	res = -ENOENT;	if (!IS_DEADDIR(inode)) {		ctx->pos = file->f_pos;		res = file->f_op->iterate_shared(file, ctx);		file->f_pos = ctx->pos;		fsnotify_access(file);		file_accessed(file);	}	inode_unlock_shared(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[];}; 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;	scoped_user_write_access_size(dirent, dirent_size(dirent, namlen + 1), efault) {		unsafe_put_user(d_ino, &dirent->d_ino, efault);		unsafe_put_user(offset, &dirent->d_offset, efault);		unsafe_put_user(namlen, &dirent->d_namlen, efault);		unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);	}	return true;efault:	buf->result = -EFAULT;	return false;} SYSCALL_DEFINE3(old_readdir, unsigned int, fd,		struct old_linux_dirent __user *, dirent, unsigned int, count){	int error;	CLASS(fd_pos, f)(fd);	struct readdir_callback buf = {		.ctx.actor = fillonedir,		.ctx.count = 1, /* Hint to fs: just one entry. */		.dirent = dirent	}; 	if (fd_empty(f))		return -EBADF; 	error = iterate_dir(fd_file(f), &buf.ctx);	if (buf.result)		error = buf.result; 	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[];}; struct getdents_callback {	struct dir_context ctx;	struct linux_dirent __user * current_dir;	int prev_reclen;	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(dirent_size(dirent, namlen + 2), sizeof(long));	int prev_reclen;	unsigned int flags = d_type; 	BUILD_BUG_ON(FILLDIR_FLAG_NOINTR & S_DT_MASK);	d_type &= S_DT_MASK; 	buf->error = verify_dirent_name(name, namlen);	if (unlikely(buf->error))		return false;	buf->error = -EINVAL;	/* only used if we fail.. */	if (reclen > ctx->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 (!(flags & FILLDIR_FLAG_NOINTR) && prev_reclen && signal_pending(current))		return false;	dirent = buf->current_dir;	prev = (void __user *) dirent - prev_reclen;	scoped_user_write_access_size(prev, reclen + prev_reclen, efault) {		/* This might be 'dirent->d_off', but if so it will get overwritten */		unsafe_put_user(offset, &prev->d_off, efault);		unsafe_put_user(d_ino, &dirent->d_ino, efault);		unsafe_put_user(reclen, &dirent->d_reclen, efault);		unsafe_put_user(d_type, (char __user *)dirent + reclen - 1, efault);		unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);	} 	buf->current_dir = (void __user *)dirent + reclen;	buf->prev_reclen = reclen;	ctx->count -= reclen;	return true;efault:	buf->error = -EFAULT;	return false;} SYSCALL_DEFINE3(getdents, unsigned int, fd,		struct linux_dirent __user *, dirent, unsigned int, count){	CLASS(fd_pos, f)(fd);	struct getdents_callback buf = {		.ctx.actor = filldir,		.ctx.count = count,		.ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR,		.current_dir = dirent	};	int error; 	if (fd_empty(f))		return -EBADF; 	error = iterate_dir(fd_file(f), &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.ctx.count;	}	return error;} struct getdents_callback64 {	struct dir_context ctx;	struct linux_dirent64 __user * current_dir;	int prev_reclen;	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(dirent_size(dirent, namlen + 1), sizeof(u64));	int prev_reclen;	unsigned int flags = d_type; 	BUILD_BUG_ON(FILLDIR_FLAG_NOINTR & S_DT_MASK);	d_type &= S_DT_MASK; 	buf->error = verify_dirent_name(name, namlen);	if (unlikely(buf->error))		return false;	buf->error = -EINVAL;	/* only used if we fail.. */	if (reclen > ctx->count)		return false;	prev_reclen = buf->prev_reclen;	if (!(flags & FILLDIR_FLAG_NOINTR) && prev_reclen && signal_pending(current))		return false;	dirent = buf->current_dir;	prev = (void __user *)dirent - prev_reclen;	scoped_user_write_access_size(prev, reclen + prev_reclen, efault) {		/* This might be 'dirent->d_off', but if so it will get overwritten */		unsafe_put_user(offset, &prev->d_off, efault);		unsafe_put_user(ino, &dirent->d_ino, efault);		unsafe_put_user(reclen, &dirent->d_reclen, efault);		unsafe_put_user(d_type, &dirent->d_type, efault);		unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);	} 	buf->prev_reclen = reclen;	buf->current_dir = (void __user *)dirent + reclen;	ctx->count -= reclen;	return true; efault:	buf->error = -EFAULT;	return false;} SYSCALL_DEFINE3(getdents64, unsigned int, fd,		struct linux_dirent64 __user *, dirent, unsigned int, count){	CLASS(fd_pos, f)(fd);	struct getdents_callback64 buf = {		.ctx.actor = filldir64,		.ctx.count = count,		.ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR,		.current_dir = dirent	};	int error; 	if (fd_empty(f))		return -EBADF; 	error = iterate_dir(fd_file(f), &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.ctx.count;	}	return error;} #ifdef CONFIG_COMPATstruct compat_old_linux_dirent {	compat_ulong_t	d_ino;	compat_ulong_t	d_offset;	unsigned short	d_namlen;	char		d_name[];}; 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;	scoped_user_write_access_size(dirent, dirent_size(dirent, namlen + 1), efault) {		unsafe_put_user(d_ino, &dirent->d_ino, efault);		unsafe_put_user(offset, &dirent->d_offset, efault);		unsafe_put_user(namlen, &dirent->d_namlen, efault);		unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);	}	return true;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;	CLASS(fd_pos, f)(fd);	struct compat_readdir_callback buf = {		.ctx.actor = compat_fillonedir,		.ctx.count = 1, /* Hint to fs: just one entry. */		.dirent = dirent	}; 	if (fd_empty(f))		return -EBADF; 	error = iterate_dir(fd_file(f), &buf.ctx);	if (buf.result)		error = buf.result; 	return error;} struct compat_linux_dirent {	compat_ulong_t	d_ino;	compat_ulong_t	d_off;	unsigned short	d_reclen;	char		d_name[];}; struct compat_getdents_callback {	struct dir_context ctx;	struct compat_linux_dirent __user *current_dir;	int prev_reclen;	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;

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