summaryrefslogtreecommitdiff
path: root/fs/verity/read_metadata.c
blob: 6ee849dc7bc183c0f55212cb5a5639fe2d134e19 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
// 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(page);
		if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) {
			kunmap(page);
			put_page(page);
			err = -EFAULT;
			break;
		}
		kunmap(page);
		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);