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