diff options
Diffstat (limited to 'include/linux/fsverity.h')
| -rw-r--r-- | include/linux/fsverity.h | 188 |
1 files changed, 164 insertions, 24 deletions
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index 78201a6d35f6..5bc7280425a7 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -12,10 +12,30 @@ #define _LINUX_FSVERITY_H #include <linux/fs.h> +#include <linux/mm.h> +#include <crypto/hash_info.h> +#include <crypto/sha2.h> #include <uapi/linux/fsverity.h> +/* + * Largest digest size among all hash algorithms supported by fs-verity. + * Currently assumed to be <= size of fsverity_descriptor::root_hash. + */ +#define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE + +/* Arbitrary limit to bound the kmalloc() size. Can be changed. */ +#define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 + +struct fsverity_info; + /* Verity operations for filesystems */ struct fsverity_operations { + /** + * The offset of the pointer to struct fsverity_info in the + * filesystem-specific part of the inode, relative to the beginning of + * the common part of the inode (the 'struct inode'). + */ + ptrdiff_t inode_info_offs; /** * Begin enabling verity on the given file. @@ -82,8 +102,7 @@ struct fsverity_operations { * isn't already cached. Implementations may ignore this * argument; it's only a performance optimization. * - * This can be called at any time on an open verity file, as well as - * between ->begin_enable_verity() and ->end_enable_verity(). It may be + * This can be called at any time on an open verity file. It may be * called by multiple processes concurrently, even with the same page. * * Note that this must retrieve a *page*, not necessarily a *block*. @@ -98,9 +117,9 @@ struct fsverity_operations { * Write a Merkle tree block to the given inode. * * @inode: the inode for which the Merkle tree is being built - * @buf: block to write - * @index: 0-based index of the block within the Merkle tree - * @log_blocksize: log base 2 of the Merkle tree block size + * @buf: the Merkle tree block to write + * @pos: the position of the block in the Merkle tree (in bytes) + * @size: the Merkle tree block size (in bytes) * * This is only called between ->begin_enable_verity() and * ->end_enable_verity(). @@ -108,15 +127,42 @@ struct fsverity_operations { * Return: 0 on success, -errno on failure */ int (*write_merkle_tree_block)(struct inode *inode, const void *buf, - u64 index, int log_blocksize); + u64 pos, unsigned int size); }; #ifdef CONFIG_FS_VERITY +/* + * Returns the address of the verity info pointer within the filesystem-specific + * part of the inode. (To save memory on filesystems that don't support + * fsverity, a field in 'struct inode' itself is no longer used.) + */ +static inline struct fsverity_info ** +fsverity_info_addr(const struct inode *inode) +{ + VFS_WARN_ON_ONCE(inode->i_sb->s_vop->inode_info_offs == 0); + return (void *)inode + inode->i_sb->s_vop->inode_info_offs; +} + static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) { - /* pairs with the cmpxchg() in fsverity_set_info() */ - return READ_ONCE(inode->i_verity_info); + /* + * Since this function can be called on inodes belonging to filesystems + * that don't support fsverity at all, and fsverity_info_addr() doesn't + * work on such filesystems, we have to start with an IS_VERITY() check. + * Checking IS_VERITY() here is also useful to minimize the overhead of + * fsverity_active() on non-verity files. + */ + if (!IS_VERITY(inode)) + return NULL; + + /* + * Pairs with the cmpxchg_release() in fsverity_set_info(). I.e., + * another task may publish the inode's verity info concurrently, + * executing a RELEASE barrier. Use smp_load_acquire() here to safely + * ACQUIRE the memory the other task published. + */ + return smp_load_acquire(fsverity_info_addr(inode)); } /* enable.c */ @@ -126,16 +172,42 @@ int fsverity_ioctl_enable(struct file *filp, const void __user *arg); /* measure.c */ int fsverity_ioctl_measure(struct file *filp, void __user *arg); +int fsverity_get_digest(struct inode *inode, + u8 raw_digest[FS_VERITY_MAX_DIGEST_SIZE], + u8 *alg, enum hash_algo *halg); /* open.c */ -int fsverity_file_open(struct inode *inode, struct file *filp); -int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); -void fsverity_cleanup_inode(struct inode *inode); +int __fsverity_file_open(struct inode *inode, struct file *filp); +int __fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); +void __fsverity_cleanup_inode(struct inode *inode); + +/** + * fsverity_cleanup_inode() - free the inode's verity info, if present + * @inode: an inode being evicted + * + * Filesystems must call this on inode eviction to free the inode's verity info. + */ +static inline void fsverity_cleanup_inode(struct inode *inode) +{ + /* + * Only IS_VERITY() inodes can have verity info, so start by checking + * for IS_VERITY() (which is faster than retrieving the pointer to the + * verity info). This minimizes overhead for non-verity inodes. + */ + if (IS_VERITY(inode)) + __fsverity_cleanup_inode(inode); + else + VFS_WARN_ON_ONCE(*fsverity_info_addr(inode) != NULL); +} + +/* read_metadata.c */ + +int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg); /* verify.c */ -bool fsverity_verify_page(struct page *page); +bool fsverity_verify_blocks(struct folio *folio, size_t len, size_t offset); void fsverity_verify_bio(struct bio *bio); void fsverity_enqueue_verify_work(struct work_struct *work); @@ -161,53 +233,83 @@ static inline int fsverity_ioctl_measure(struct file *filp, void __user *arg) return -EOPNOTSUPP; } +static inline int fsverity_get_digest(struct inode *inode, + u8 raw_digest[FS_VERITY_MAX_DIGEST_SIZE], + u8 *alg, enum hash_algo *halg) +{ + /* + * fsverity is not enabled in the kernel configuration, so always report + * that the file doesn't have fsverity enabled (digest size 0). + */ + return 0; +} + /* open.c */ -static inline int fsverity_file_open(struct inode *inode, struct file *filp) +static inline int __fsverity_file_open(struct inode *inode, struct file *filp) { - return IS_VERITY(inode) ? -EOPNOTSUPP : 0; + return -EOPNOTSUPP; } -static inline int fsverity_prepare_setattr(struct dentry *dentry, - struct iattr *attr) +static inline int __fsverity_prepare_setattr(struct dentry *dentry, + struct iattr *attr) { - return IS_VERITY(d_inode(dentry)) ? -EOPNOTSUPP : 0; + return -EOPNOTSUPP; } static inline void fsverity_cleanup_inode(struct inode *inode) { } +/* read_metadata.c */ + +static inline int fsverity_ioctl_read_metadata(struct file *filp, + const void __user *uarg) +{ + return -EOPNOTSUPP; +} + /* verify.c */ -static inline bool fsverity_verify_page(struct page *page) +static inline bool fsverity_verify_blocks(struct folio *folio, size_t len, + size_t offset) { - WARN_ON(1); + WARN_ON_ONCE(1); return false; } static inline void fsverity_verify_bio(struct bio *bio) { - WARN_ON(1); + WARN_ON_ONCE(1); } static inline void fsverity_enqueue_verify_work(struct work_struct *work) { - WARN_ON(1); + WARN_ON_ONCE(1); } #endif /* !CONFIG_FS_VERITY */ +static inline bool fsverity_verify_folio(struct folio *folio) +{ + return fsverity_verify_blocks(folio, folio_size(folio), 0); +} + +static inline bool fsverity_verify_page(struct page *page) +{ + return fsverity_verify_blocks(page_folio(page), PAGE_SIZE, 0); +} + /** * fsverity_active() - do reads from the inode need to go through fs-verity? * @inode: inode to check * - * This checks whether ->i_verity_info has been set. + * This checks whether the inode's verity info has been set. * - * Filesystems call this from ->readpages() to check whether the pages need to + * Filesystems call this from ->readahead() to check whether the pages need to * be verified or not. Don't use IS_VERITY() for this purpose; it's subject to * a race condition where the file is being read concurrently with - * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before ->i_verity_info.) + * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before the verity info.) * * Return: true if reads need to go through fs-verity, otherwise false */ @@ -216,4 +318,42 @@ static inline bool fsverity_active(const struct inode *inode) return fsverity_get_info(inode) != NULL; } +/** + * fsverity_file_open() - prepare to open a verity file + * @inode: the inode being opened + * @filp: the struct file being set up + * + * When opening a verity file, deny the open if it is for writing. Otherwise, + * set up the inode's verity info if not already done. + * + * When combined with fscrypt, this must be called after fscrypt_file_open(). + * Otherwise, we won't have the key set up to decrypt the verity metadata. + * + * Return: 0 on success, -errno on failure + */ +static inline int fsverity_file_open(struct inode *inode, struct file *filp) +{ + if (IS_VERITY(inode)) + return __fsverity_file_open(inode, filp); + return 0; +} + +/** + * fsverity_prepare_setattr() - prepare to change a verity inode's attributes + * @dentry: dentry through which the inode is being changed + * @attr: attributes to change + * + * Verity files are immutable, so deny truncates. This isn't covered by the + * open-time check because sys_truncate() takes a path, not a file descriptor. + * + * Return: 0 on success, -errno on failure + */ +static inline int fsverity_prepare_setattr(struct dentry *dentry, + struct iattr *attr) +{ + if (IS_VERITY(d_inode(dentry))) + return __fsverity_prepare_setattr(dentry, attr); + return 0; +} + #endif /* _LINUX_FSVERITY_H */ |