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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Ioctl to read verity metadata
- *
- * Copyright 2021 Google LLC
- */
- #include "fsverity_private.h"
- #include <linux/backing-dev.h>
- #include <linux/highmem.h>
- #include <linux/sched/signal.h>
- #include <linux/uaccess.h>
- static int fsverity_read_merkle_tree(struct inode *inode,
- const struct fsverity_info *vi,
- void __user *buf, u64 offset, int length)
- {
- const struct fsverity_operations *vops = inode->i_sb->s_vop;
- u64 end_offset;
- unsigned int offs_in_page;
- pgoff_t index, last_index;
- int retval = 0;
- int err = 0;
- end_offset = min(offset + length, vi->tree_params.tree_size);
- if (offset >= end_offset)
- return 0;
- offs_in_page = offset_in_page(offset);
- last_index = (end_offset - 1) >> PAGE_SHIFT;
- /*
- * Iterate through each Merkle tree page in the requested range and copy
- * the requested portion to userspace. Note that the Merkle tree block
- * size isn't important here, as we are returning a byte stream; i.e.,
- * we can just work with pages even if the tree block size != PAGE_SIZE.
- */
- for (index = offset >> PAGE_SHIFT; index <= last_index; index++) {
- unsigned long num_ra_pages =
- min_t(unsigned long, last_index - index + 1,
- inode->i_sb->s_bdi->io_pages);
- unsigned int bytes_to_copy = min_t(u64, end_offset - offset,
- PAGE_SIZE - offs_in_page);
- struct page *page;
- const void *virt;
- page = vops->read_merkle_tree_page(inode, index, num_ra_pages);
- if (IS_ERR(page)) {
- err = PTR_ERR(page);
- fsverity_err(inode,
- "Error %d reading Merkle tree page %lu",
- err, index);
- break;
- }
- virt = kmap_local_page(page);
- if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) {
- kunmap_local(virt);
- put_page(page);
- err = -EFAULT;
- break;
- }
- kunmap_local(virt);
- put_page(page);
- retval += bytes_to_copy;
- buf += bytes_to_copy;
- offset += bytes_to_copy;
- if (fatal_signal_pending(current)) {
- err = -EINTR;
- break;
- }
- cond_resched();
- offs_in_page = 0;
- }
- return retval ? retval : err;
- }
- /* Copy the requested portion of the buffer to userspace. */
- static int fsverity_read_buffer(void __user *dst, u64 offset, int length,
- const void *src, size_t src_length)
- {
- if (offset >= src_length)
- return 0;
- src += offset;
- src_length -= offset;
- length = min_t(size_t, length, src_length);
- if (copy_to_user(dst, src, length))
- return -EFAULT;
- return length;
- }
- static int fsverity_read_descriptor(struct inode *inode,
- void __user *buf, u64 offset, int length)
- {
- struct fsverity_descriptor *desc;
- size_t desc_size;
- int res;
- res = fsverity_get_descriptor(inode, &desc);
- if (res)
- return res;
- /* don't include the signature */
- desc_size = offsetof(struct fsverity_descriptor, signature);
- desc->sig_size = 0;
- res = fsverity_read_buffer(buf, offset, length, desc, desc_size);
- kfree(desc);
- return res;
- }
- static int fsverity_read_signature(struct inode *inode,
- void __user *buf, u64 offset, int length)
- {
- struct fsverity_descriptor *desc;
- int res;
- res = fsverity_get_descriptor(inode, &desc);
- if (res)
- return res;
- if (desc->sig_size == 0) {
- res = -ENODATA;
- goto out;
- }
- /*
- * Include only the signature. Note that fsverity_get_descriptor()
- * already verified that sig_size is in-bounds.
- */
- res = fsverity_read_buffer(buf, offset, length, desc->signature,
- le32_to_cpu(desc->sig_size));
- out:
- kfree(desc);
- return res;
- }
- /**
- * fsverity_ioctl_read_metadata() - read verity metadata from a file
- * @filp: file to read the metadata from
- * @uarg: user pointer to fsverity_read_metadata_arg
- *
- * Return: length read on success, 0 on EOF, -errno on failure
- */
- int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg)
- {
- struct inode *inode = file_inode(filp);
- const struct fsverity_info *vi;
- struct fsverity_read_metadata_arg arg;
- int length;
- void __user *buf;
- vi = fsverity_get_info(inode);
- if (!vi)
- return -ENODATA; /* not a verity file */
- /*
- * Note that we don't have to explicitly check that the file is open for
- * reading, since verity files can only be opened for reading.
- */
- if (copy_from_user(&arg, uarg, sizeof(arg)))
- return -EFAULT;
- if (arg.__reserved)
- return -EINVAL;
- /* offset + length must not overflow. */
- if (arg.offset + arg.length < arg.offset)
- return -EINVAL;
- /* Ensure that the return value will fit in INT_MAX. */
- length = min_t(u64, arg.length, INT_MAX);
- buf = u64_to_user_ptr(arg.buf_ptr);
- switch (arg.metadata_type) {
- case FS_VERITY_METADATA_TYPE_MERKLE_TREE:
- return fsverity_read_merkle_tree(inode, vi, buf, arg.offset,
- length);
- case FS_VERITY_METADATA_TYPE_DESCRIPTOR:
- return fsverity_read_descriptor(inode, buf, arg.offset, length);
- case FS_VERITY_METADATA_TYPE_SIGNATURE:
- return fsverity_read_signature(inode, buf, arg.offset, length);
- default:
- return -EINVAL;
- }
- }
- EXPORT_SYMBOL_GPL(fsverity_ioctl_read_metadata);
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