From 2a7349add18e5915cd87251af5f98db1772b6131 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 10 Aug 2025 00:57:01 -0700 Subject: fsverity: add support for info in fs-specific part of inode Add an inode_info_offs field to struct fsverity_operations, and update fs/verity/ to support it. When set to a nonzero value, it specifies the offset to the fsverity_info pointer within the filesystem-specific part of the inode structure, to be used instead of inode::i_verity_info. Since this makes inode::i_verity_info no longer necessarily used, update comments that mentioned it. This is a prerequisite for a later commit that removes inode::i_verity_info, saving memory and improving cache efficiency on filesystems that don't support fsverity. Co-developed-by: Christian Brauner Signed-off-by: Eric Biggers Link: https://lore.kernel.org/20250810075706.172910-9-ebiggers@kernel.org Signed-off-by: Christian Brauner --- include/linux/fsverity.h | 44 ++++++++++++++++++++++++++++++++++---------- 1 file changed, 34 insertions(+), 10 deletions(-) (limited to 'include/linux') diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index 1eb7eae580be..e0f132cb7839 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -28,6 +28,12 @@ /* 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. @@ -124,15 +130,33 @@ struct fsverity_operations { #ifdef CONFIG_FS_VERITY +static inline struct fsverity_info ** +fsverity_info_addr(const struct inode *inode) +{ + if (inode->i_sb->s_vop->inode_info_offs == 0) + return (struct fsverity_info **)&inode->i_verity_info; + 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_release() in fsverity_set_info(). - * I.e., another task may publish ->i_verity_info concurrently, - * executing a RELEASE barrier. We need to use smp_load_acquire() here - * to safely ACQUIRE the memory the other task published. + * 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(&inode->i_verity_info); + return smp_load_acquire(fsverity_info_addr(inode)); } /* enable.c */ @@ -156,11 +180,11 @@ 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 ->i_verity_info. + * Filesystems must call this on inode eviction to free the inode's verity info. */ static inline void fsverity_cleanup_inode(struct inode *inode) { - if (inode->i_verity_info) + if (*fsverity_info_addr(inode)) __fsverity_cleanup_inode(inode); } @@ -267,12 +291,12 @@ static inline bool fsverity_verify_page(struct page *page) * 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 ->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 */ @@ -287,7 +311,7 @@ static inline bool fsverity_active(const struct inode *inode) * @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 ->i_verity_info if not already done. + * 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. -- cgit v1.2.3