// SPDX-License-Identifier: GPL-2.0-only#include <linux/fs.h>#include <linux/fs_struct.h>#include <linux/kernel_read_file.h>#include <linux/security.h>#include <linux/vmalloc.h> /** * kernel_read_file() - read file contents into a kernel buffer * * @file	file to read from * @offset	where to start reading from (see below). * @buf		pointer to a "void *" buffer for reading into (if *		*@buf is NULL, a buffer will be allocated, and *		@buf_size will be ignored) * @buf_size	size of buf, if already allocated. If @buf not *		allocated, this is the largest size to allocate. * @file_size	if non-NULL, the full size of @file will be *		written here. * @id		the kernel_read_file_id identifying the type of *		file contents being read (for LSMs to examine) * * @offset must be 0 unless both @buf and @file_size are non-NULL * (i.e. the caller must be expecting to read partial file contents * via an already-allocated @buf, in at most @buf_size chunks, and * will be able to determine when the entire file was read by * checking @file_size). This isn't a recommended way to read a * file, though, since it is possible that the contents might * change between calls to kernel_read_file(). * * Returns number of bytes read (no single read will be bigger * than INT_MAX), or negative on error. * */int kernel_read_file(struct file *file, loff_t offset, void **buf,		     size_t buf_size, size_t *file_size,		     enum kernel_read_file_id id){	loff_t i_size, pos;	size_t copied;	void *allocated = NULL;	bool whole_file;	int ret; 	if (offset != 0 && (!*buf || !file_size))		return -EINVAL; 	if (!S_ISREG(file_inode(file)->i_mode))		return -EINVAL; 	ret = deny_write_access(file);	if (ret)		return ret; 	i_size = i_size_read(file_inode(file));	if (i_size <= 0) {		ret = -EINVAL;		goto out;	}	/* The file is too big for sane activities. */	if (i_size > INT_MAX) {		ret = -EFBIG;		goto out;	}	/* The entire file cannot be read in one buffer. */	if (!file_size && offset == 0 && i_size > buf_size) {		ret = -EFBIG;		goto out;	} 	whole_file = (offset == 0 && i_size <= buf_size);	ret = security_kernel_read_file(file, id, whole_file);	if (ret)		goto out; 	if (file_size)		*file_size = i_size; 	if (!*buf)		*buf = allocated = vmalloc(i_size);	if (!*buf) {		ret = -ENOMEM;		goto out;	} 	pos = offset;	copied = 0;	while (copied < buf_size) {		ssize_t bytes;		size_t wanted = min_t(size_t, buf_size - copied,					      i_size - pos); 		bytes = kernel_read(file, *buf + copied, wanted, &pos);		if (bytes < 0) {			ret = bytes;			goto out_free;		} 		if (bytes == 0)			break;		copied += bytes;	} 	if (whole_file) {		if (pos != i_size) {			ret = -EIO;			goto out_free;		} 		ret = security_kernel_post_read_file(file, *buf, i_size, id);	} out_free:	if (ret < 0) {		if (allocated) {			vfree(*buf);			*buf = NULL;		}	} out:	allow_write_access(file);	return ret == 0 ? copied : ret;}EXPORT_SYMBOL_GPL(kernel_read_file); int kernel_read_file_from_path(const char *path, loff_t offset, void **buf,			       size_t buf_size, size_t *file_size,			       enum kernel_read_file_id id){	struct file *file;	int ret; 	if (!path || !*path)		return -EINVAL; 	file = filp_open(path, O_RDONLY, 0);	if (IS_ERR(file))		return PTR_ERR(file); 	ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);	fput(file);	return ret;}EXPORT_SYMBOL_GPL(kernel_read_file_from_path); int kernel_read_file_from_path_initns(const char *path, loff_t offset,				      void **buf, size_t buf_size,				      size_t *file_size,				      enum kernel_read_file_id id){	struct file *file;	struct path root;	int ret; 	if (!path || !*path)		return -EINVAL; 	task_lock(&init_task);	get_fs_root(init_task.fs, &root);	task_unlock(&init_task); 	file = file_open_root(root.dentry, root.mnt, path, O_RDONLY, 0);	path_put(&root);	if (IS_ERR(file))		return PTR_ERR(file); 	ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);	fput(file);	return ret;}EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns); int kernel_read_file_from_fd(int fd, loff_t offset, void **buf,			     size_t buf_size, size_t *file_size,			     enum kernel_read_file_id id){	struct fd f = fdget(fd);	int ret = -EBADF; 	if (!f.file)		goto out; 	ret = kernel_read_file(f.file, offset, buf, buf_size, file_size, id);out:	fdput(f);	return ret;}EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);