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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 builtin 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 builtin signature. 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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