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1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | /* | |
3 | * fs-verity: read-only file-based authenticity protection | |
4 | * | |
5 | * This header declares the interface between the fs/verity/ support layer and | |
6 | * filesystems that support fs-verity. | |
7 | * | |
8 | * Copyright 2019 Google LLC | |
9 | */ | |
10 | ||
11 | #ifndef _LINUX_FSVERITY_H | |
12 | #define _LINUX_FSVERITY_H | |
13 | ||
14 | #include <linux/fs.h> | |
15 | #include <uapi/linux/fsverity.h> | |
16 | ||
17 | /* Verity operations for filesystems */ | |
18 | struct fsverity_operations { | |
19 | ||
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20 | /** |
21 | * Begin enabling verity on the given file. | |
22 | * | |
23 | * @filp: a readonly file descriptor for the file | |
24 | * | |
25 | * The filesystem must do any needed filesystem-specific preparations | |
26 | * for enabling verity, e.g. evicting inline data. It also must return | |
27 | * -EBUSY if verity is already being enabled on the given file. | |
28 | * | |
29 | * i_rwsem is held for write. | |
30 | * | |
31 | * Return: 0 on success, -errno on failure | |
32 | */ | |
33 | int (*begin_enable_verity)(struct file *filp); | |
34 | ||
35 | /** | |
36 | * End enabling verity on the given file. | |
37 | * | |
38 | * @filp: a readonly file descriptor for the file | |
39 | * @desc: the verity descriptor to write, or NULL on failure | |
40 | * @desc_size: size of verity descriptor, or 0 on failure | |
41 | * @merkle_tree_size: total bytes the Merkle tree took up | |
42 | * | |
43 | * If desc == NULL, then enabling verity failed and the filesystem only | |
44 | * must do any necessary cleanups. Else, it must also store the given | |
45 | * verity descriptor to a fs-specific location associated with the inode | |
46 | * and do any fs-specific actions needed to mark the inode as a verity | |
47 | * inode, e.g. setting a bit in the on-disk inode. The filesystem is | |
48 | * also responsible for setting the S_VERITY flag in the VFS inode. | |
49 | * | |
50 | * i_rwsem is held for write, but it may have been dropped between | |
51 | * ->begin_enable_verity() and ->end_enable_verity(). | |
52 | * | |
53 | * Return: 0 on success, -errno on failure | |
54 | */ | |
55 | int (*end_enable_verity)(struct file *filp, const void *desc, | |
56 | size_t desc_size, u64 merkle_tree_size); | |
57 | ||
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58 | /** |
59 | * Get the verity descriptor of the given inode. | |
60 | * | |
61 | * @inode: an inode with the S_VERITY flag set | |
62 | * @buf: buffer in which to place the verity descriptor | |
63 | * @bufsize: size of @buf, or 0 to retrieve the size only | |
64 | * | |
65 | * If bufsize == 0, then the size of the verity descriptor is returned. | |
66 | * Otherwise the verity descriptor is written to 'buf' and its actual | |
67 | * size is returned; -ERANGE is returned if it's too large. This may be | |
68 | * called by multiple processes concurrently on the same inode. | |
69 | * | |
70 | * Return: the size on success, -errno on failure | |
71 | */ | |
72 | int (*get_verity_descriptor)(struct inode *inode, void *buf, | |
73 | size_t bufsize); | |
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74 | |
75 | /** | |
76 | * Read a Merkle tree page of the given inode. | |
77 | * | |
78 | * @inode: the inode | |
79 | * @index: 0-based index of the page within the Merkle tree | |
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80 | * @num_ra_pages: The number of Merkle tree pages that should be |
81 | * prefetched starting at @index if the page at @index | |
82 | * isn't already cached. Implementations may ignore this | |
83 | * argument; it's only a performance optimization. | |
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84 | * |
85 | * This can be called at any time on an open verity file, as well as | |
86 | * between ->begin_enable_verity() and ->end_enable_verity(). It may be | |
87 | * called by multiple processes concurrently, even with the same page. | |
88 | * | |
89 | * Note that this must retrieve a *page*, not necessarily a *block*. | |
90 | * | |
91 | * Return: the page on success, ERR_PTR() on failure | |
92 | */ | |
93 | struct page *(*read_merkle_tree_page)(struct inode *inode, | |
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94 | pgoff_t index, |
95 | unsigned long num_ra_pages); | |
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96 | |
97 | /** | |
98 | * Write a Merkle tree block to the given inode. | |
99 | * | |
100 | * @inode: the inode for which the Merkle tree is being built | |
101 | * @buf: block to write | |
102 | * @index: 0-based index of the block within the Merkle tree | |
103 | * @log_blocksize: log base 2 of the Merkle tree block size | |
104 | * | |
105 | * This is only called between ->begin_enable_verity() and | |
106 | * ->end_enable_verity(). | |
107 | * | |
108 | * Return: 0 on success, -errno on failure | |
109 | */ | |
110 | int (*write_merkle_tree_block)(struct inode *inode, const void *buf, | |
111 | u64 index, int log_blocksize); | |
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112 | }; |
113 | ||
114 | #ifdef CONFIG_FS_VERITY | |
115 | ||
116 | static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) | |
117 | { | |
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118 | /* |
119 | * Pairs with the cmpxchg_release() in fsverity_set_info(). | |
120 | * I.e., another task may publish ->i_verity_info concurrently, | |
121 | * executing a RELEASE barrier. We need to use smp_load_acquire() here | |
122 | * to safely ACQUIRE the memory the other task published. | |
123 | */ | |
124 | return smp_load_acquire(&inode->i_verity_info); | |
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125 | } |
126 | ||
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127 | /* enable.c */ |
128 | ||
9cd6b593 | 129 | int fsverity_ioctl_enable(struct file *filp, const void __user *arg); |
3fda4c61 | 130 | |
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131 | /* measure.c */ |
132 | ||
9cd6b593 | 133 | int fsverity_ioctl_measure(struct file *filp, void __user *arg); |
4dd893d8 | 134 | |
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135 | /* open.c */ |
136 | ||
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137 | int fsverity_file_open(struct inode *inode, struct file *filp); |
138 | int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); | |
139 | void fsverity_cleanup_inode(struct inode *inode); | |
fd2d1acf | 140 | |
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141 | /* read_metadata.c */ |
142 | ||
143 | int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg); | |
144 | ||
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145 | /* verify.c */ |
146 | ||
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147 | bool fsverity_verify_page(struct page *page); |
148 | void fsverity_verify_bio(struct bio *bio); | |
149 | void fsverity_enqueue_verify_work(struct work_struct *work); | |
8a1d0f9c | 150 | |
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151 | #else /* !CONFIG_FS_VERITY */ |
152 | ||
153 | static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) | |
154 | { | |
155 | return NULL; | |
156 | } | |
157 | ||
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158 | /* enable.c */ |
159 | ||
160 | static inline int fsverity_ioctl_enable(struct file *filp, | |
161 | const void __user *arg) | |
162 | { | |
163 | return -EOPNOTSUPP; | |
164 | } | |
165 | ||
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166 | /* measure.c */ |
167 | ||
168 | static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg) | |
169 | { | |
170 | return -EOPNOTSUPP; | |
171 | } | |
172 | ||
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173 | /* open.c */ |
174 | ||
175 | static inline int fsverity_file_open(struct inode *inode, struct file *filp) | |
176 | { | |
177 | return IS_VERITY(inode) ? -EOPNOTSUPP : 0; | |
178 | } | |
179 | ||
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180 | static inline int fsverity_prepare_setattr(struct dentry *dentry, |
181 | struct iattr *attr) | |
182 | { | |
183 | return IS_VERITY(d_inode(dentry)) ? -EOPNOTSUPP : 0; | |
184 | } | |
185 | ||
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186 | static inline void fsverity_cleanup_inode(struct inode *inode) |
187 | { | |
188 | } | |
189 | ||
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190 | /* read_metadata.c */ |
191 | ||
192 | static inline int fsverity_ioctl_read_metadata(struct file *filp, | |
193 | const void __user *uarg) | |
194 | { | |
195 | return -EOPNOTSUPP; | |
196 | } | |
197 | ||
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198 | /* verify.c */ |
199 | ||
200 | static inline bool fsverity_verify_page(struct page *page) | |
201 | { | |
202 | WARN_ON(1); | |
203 | return false; | |
204 | } | |
205 | ||
206 | static inline void fsverity_verify_bio(struct bio *bio) | |
207 | { | |
208 | WARN_ON(1); | |
209 | } | |
210 | ||
211 | static inline void fsverity_enqueue_verify_work(struct work_struct *work) | |
212 | { | |
213 | WARN_ON(1); | |
214 | } | |
215 | ||
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216 | #endif /* !CONFIG_FS_VERITY */ |
217 | ||
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218 | /** |
219 | * fsverity_active() - do reads from the inode need to go through fs-verity? | |
6377a38b | 220 | * @inode: inode to check |
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221 | * |
222 | * This checks whether ->i_verity_info has been set. | |
223 | * | |
224 | * Filesystems call this from ->readpages() to check whether the pages need to | |
225 | * be verified or not. Don't use IS_VERITY() for this purpose; it's subject to | |
226 | * a race condition where the file is being read concurrently with | |
227 | * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before ->i_verity_info.) | |
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228 | * |
229 | * Return: true if reads need to go through fs-verity, otherwise false | |
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230 | */ |
231 | static inline bool fsverity_active(const struct inode *inode) | |
232 | { | |
233 | return fsverity_get_info(inode) != NULL; | |
234 | } | |
235 | ||
fd2d1acf | 236 | #endif /* _LINUX_FSVERITY_H */ |