// 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 SSIZE_MAX), or negative on error. * */ ssize_t 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; ssize_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 > SSIZE_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); ssize_t 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; ssize_t 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); ssize_t 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; ssize_t 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, 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); ssize_t 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); ssize_t ret = -EBADF; if (!f.file || !(f.file->f_mode & FMODE_READ)) 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);