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1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* | |
3 | * Ioctl to read verity metadata | |
4 | * | |
5 | * Copyright 2021 Google LLC | |
6 | */ | |
7 | ||
8 | #include "fsverity_private.h" | |
9 | ||
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10 | #include <linux/backing-dev.h> |
11 | #include <linux/highmem.h> | |
12 | #include <linux/sched/signal.h> | |
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13 | #include <linux/uaccess.h> |
14 | ||
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15 | static int fsverity_read_merkle_tree(struct inode *inode, |
16 | const struct fsverity_info *vi, | |
17 | void __user *buf, u64 offset, int length) | |
18 | { | |
19 | const struct fsverity_operations *vops = inode->i_sb->s_vop; | |
20 | u64 end_offset; | |
21 | unsigned int offs_in_page; | |
22 | pgoff_t index, last_index; | |
23 | int retval = 0; | |
24 | int err = 0; | |
25 | ||
26 | end_offset = min(offset + length, vi->tree_params.tree_size); | |
27 | if (offset >= end_offset) | |
28 | return 0; | |
29 | offs_in_page = offset_in_page(offset); | |
30 | last_index = (end_offset - 1) >> PAGE_SHIFT; | |
31 | ||
32 | /* | |
33 | * Iterate through each Merkle tree page in the requested range and copy | |
34 | * the requested portion to userspace. Note that the Merkle tree block | |
35 | * size isn't important here, as we are returning a byte stream; i.e., | |
36 | * we can just work with pages even if the tree block size != PAGE_SIZE. | |
37 | */ | |
38 | for (index = offset >> PAGE_SHIFT; index <= last_index; index++) { | |
39 | unsigned long num_ra_pages = | |
40 | min_t(unsigned long, last_index - index + 1, | |
41 | inode->i_sb->s_bdi->io_pages); | |
42 | unsigned int bytes_to_copy = min_t(u64, end_offset - offset, | |
43 | PAGE_SIZE - offs_in_page); | |
44 | struct page *page; | |
45 | const void *virt; | |
46 | ||
47 | page = vops->read_merkle_tree_page(inode, index, num_ra_pages); | |
48 | if (IS_ERR(page)) { | |
49 | err = PTR_ERR(page); | |
50 | fsverity_err(inode, | |
51 | "Error %d reading Merkle tree page %lu", | |
52 | err, index); | |
53 | break; | |
54 | } | |
55 | ||
56 | virt = kmap(page); | |
57 | if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) { | |
58 | kunmap(page); | |
59 | put_page(page); | |
60 | err = -EFAULT; | |
61 | break; | |
62 | } | |
63 | kunmap(page); | |
64 | put_page(page); | |
65 | ||
66 | retval += bytes_to_copy; | |
67 | buf += bytes_to_copy; | |
68 | offset += bytes_to_copy; | |
69 | ||
70 | if (fatal_signal_pending(current)) { | |
71 | err = -EINTR; | |
72 | break; | |
73 | } | |
74 | cond_resched(); | |
75 | offs_in_page = 0; | |
76 | } | |
77 | return retval ? retval : err; | |
78 | } | |
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79 | |
80 | /* Copy the requested portion of the buffer to userspace. */ | |
81 | static int fsverity_read_buffer(void __user *dst, u64 offset, int length, | |
82 | const void *src, size_t src_length) | |
83 | { | |
84 | if (offset >= src_length) | |
85 | return 0; | |
86 | src += offset; | |
87 | src_length -= offset; | |
88 | ||
89 | length = min_t(size_t, length, src_length); | |
90 | ||
91 | if (copy_to_user(dst, src, length)) | |
92 | return -EFAULT; | |
93 | ||
94 | return length; | |
95 | } | |
96 | ||
97 | static int fsverity_read_descriptor(struct inode *inode, | |
98 | void __user *buf, u64 offset, int length) | |
99 | { | |
100 | struct fsverity_descriptor *desc; | |
101 | size_t desc_size; | |
102 | int res; | |
103 | ||
104 | res = fsverity_get_descriptor(inode, &desc, &desc_size); | |
105 | if (res) | |
106 | return res; | |
107 | ||
108 | /* don't include the signature */ | |
109 | desc_size = offsetof(struct fsverity_descriptor, signature); | |
110 | desc->sig_size = 0; | |
111 | ||
112 | res = fsverity_read_buffer(buf, offset, length, desc, desc_size); | |
113 | ||
114 | kfree(desc); | |
115 | return res; | |
116 | } | |
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117 | |
118 | static int fsverity_read_signature(struct inode *inode, | |
119 | void __user *buf, u64 offset, int length) | |
120 | { | |
121 | struct fsverity_descriptor *desc; | |
122 | size_t desc_size; | |
123 | int res; | |
124 | ||
125 | res = fsverity_get_descriptor(inode, &desc, &desc_size); | |
126 | if (res) | |
127 | return res; | |
128 | ||
129 | if (desc->sig_size == 0) { | |
130 | res = -ENODATA; | |
131 | goto out; | |
132 | } | |
133 | ||
134 | /* | |
135 | * Include only the signature. Note that fsverity_get_descriptor() | |
136 | * already verified that sig_size is in-bounds. | |
137 | */ | |
138 | res = fsverity_read_buffer(buf, offset, length, desc->signature, | |
139 | le32_to_cpu(desc->sig_size)); | |
140 | out: | |
141 | kfree(desc); | |
142 | return res; | |
143 | } | |
144 | ||
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145 | /** |
146 | * fsverity_ioctl_read_metadata() - read verity metadata from a file | |
147 | * @filp: file to read the metadata from | |
148 | * @uarg: user pointer to fsverity_read_metadata_arg | |
149 | * | |
150 | * Return: length read on success, 0 on EOF, -errno on failure | |
151 | */ | |
152 | int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) | |
153 | { | |
154 | struct inode *inode = file_inode(filp); | |
155 | const struct fsverity_info *vi; | |
156 | struct fsverity_read_metadata_arg arg; | |
157 | int length; | |
158 | void __user *buf; | |
159 | ||
160 | vi = fsverity_get_info(inode); | |
161 | if (!vi) | |
162 | return -ENODATA; /* not a verity file */ | |
163 | /* | |
164 | * Note that we don't have to explicitly check that the file is open for | |
165 | * reading, since verity files can only be opened for reading. | |
166 | */ | |
167 | ||
168 | if (copy_from_user(&arg, uarg, sizeof(arg))) | |
169 | return -EFAULT; | |
170 | ||
171 | if (arg.__reserved) | |
172 | return -EINVAL; | |
173 | ||
174 | /* offset + length must not overflow. */ | |
175 | if (arg.offset + arg.length < arg.offset) | |
176 | return -EINVAL; | |
177 | ||
178 | /* Ensure that the return value will fit in INT_MAX. */ | |
179 | length = min_t(u64, arg.length, INT_MAX); | |
180 | ||
181 | buf = u64_to_user_ptr(arg.buf_ptr); | |
182 | ||
183 | switch (arg.metadata_type) { | |
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184 | case FS_VERITY_METADATA_TYPE_MERKLE_TREE: |
185 | return fsverity_read_merkle_tree(inode, vi, buf, arg.offset, | |
186 | length); | |
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187 | case FS_VERITY_METADATA_TYPE_DESCRIPTOR: |
188 | return fsverity_read_descriptor(inode, buf, arg.offset, length); | |
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189 | case FS_VERITY_METADATA_TYPE_SIGNATURE: |
190 | return fsverity_read_signature(inode, buf, arg.offset, length); | |
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191 | default: |
192 | return -EINVAL; | |
193 | } | |
194 | } | |
195 | EXPORT_SYMBOL_GPL(fsverity_ioctl_read_metadata); |