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 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 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); 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 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. 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, 94 pgoff_t index, 95 unsigned long num_ra_pages); 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); 112 }; 113 114 #ifdef CONFIG_FS_VERITY 115 116 static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) 117 { 118 /* pairs with the cmpxchg() in fsverity_set_info() */ 119 return READ_ONCE(inode->i_verity_info); 120 } 121 122 /* enable.c */ 123 124 extern int fsverity_ioctl_enable(struct file *filp, const void __user *arg); 125 126 /* measure.c */ 127 128 extern int fsverity_ioctl_measure(struct file *filp, void __user *arg); 129 130 /* open.c */ 131 132 extern int fsverity_file_open(struct inode *inode, struct file *filp); 133 extern int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); 134 extern void fsverity_cleanup_inode(struct inode *inode); 135 136 /* verify.c */ 137 138 extern bool fsverity_verify_page(struct page *page); 139 extern void fsverity_verify_bio(struct bio *bio); 140 extern void fsverity_enqueue_verify_work(struct work_struct *work); 141 142 #else /* !CONFIG_FS_VERITY */ 143 144 static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) 145 { 146 return NULL; 147 } 148 149 /* enable.c */ 150 151 static inline int fsverity_ioctl_enable(struct file *filp, 152 const void __user *arg) 153 { 154 return -EOPNOTSUPP; 155 } 156 157 /* measure.c */ 158 159 static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg) 160 { 161 return -EOPNOTSUPP; 162 } 163 164 /* open.c */ 165 166 static inline int fsverity_file_open(struct inode *inode, struct file *filp) 167 { 168 return IS_VERITY(inode) ? -EOPNOTSUPP : 0; 169 } 170 171 static inline int fsverity_prepare_setattr(struct dentry *dentry, 172 struct iattr *attr) 173 { 174 return IS_VERITY(d_inode(dentry)) ? -EOPNOTSUPP : 0; 175 } 176 177 static inline void fsverity_cleanup_inode(struct inode *inode) 178 { 179 } 180 181 /* verify.c */ 182 183 static inline bool fsverity_verify_page(struct page *page) 184 { 185 WARN_ON(1); 186 return false; 187 } 188 189 static inline void fsverity_verify_bio(struct bio *bio) 190 { 191 WARN_ON(1); 192 } 193 194 static inline void fsverity_enqueue_verify_work(struct work_struct *work) 195 { 196 WARN_ON(1); 197 } 198 199 #endif /* !CONFIG_FS_VERITY */ 200 201 /** 202 * fsverity_active() - do reads from the inode need to go through fs-verity? 203 * 204 * This checks whether ->i_verity_info has been set. 205 * 206 * Filesystems call this from ->readpages() to check whether the pages need to 207 * be verified or not. Don't use IS_VERITY() for this purpose; it's subject to 208 * a race condition where the file is being read concurrently with 209 * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before ->i_verity_info.) 210 */ 211 static inline bool fsverity_active(const struct inode *inode) 212 { 213 return fsverity_get_info(inode) != NULL; 214 } 215 216 #endif /* _LINUX_FSVERITY_H */ 217