[PATCH v7 08/17] fs-verity: add the hook for file ->setattr()
From: Eric Biggers <ebiggers@kernel.org>
Date: 2019-07-22 16:54:09
Also in:
linux-api, linux-f2fs-devel, linux-fscrypt, linux-fsdevel, linux-integrity
Subsystem:
filesystems (vfs and infrastructure), fsverity: read-only file-based authenticity protection, the rest · Maintainers:
Alexander Viro, Christian Brauner, Eric Biggers, Theodore Y. Ts'o, Linus Torvalds
From: Eric Biggers <redacted> Add a function fsverity_prepare_setattr() which filesystems that support fs-verity must call to deny truncates of verity files. Reviewed-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> Signed-off-by: Eric Biggers <redacted> --- fs/verity/open.c | 21 +++++++++++++++++++++ include/linux/fsverity.h | 7 +++++++ 2 files changed, 28 insertions(+)
diff --git a/fs/verity/open.c b/fs/verity/open.c
index 8013f77f907eb..2cb2fe8082bff 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c@@ -295,6 +295,27 @@ int fsverity_file_open(struct inode *inode, struct file *filp) } EXPORT_SYMBOL_GPL(fsverity_file_open); +/** + * 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 + */ +int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr) +{ + if (IS_VERITY(d_inode(dentry)) && (attr->ia_valid & ATTR_SIZE)) { + pr_debug("Denying truncate of verity file (ino %lu)\n", + d_inode(dentry)->i_ino); + return -EPERM; + } + return 0; +} +EXPORT_SYMBOL_GPL(fsverity_prepare_setattr); + /** * fsverity_cleanup_inode() - free the inode's verity info, if present *
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index 09b04dab64520..cbd0f84e1620f 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h@@ -46,6 +46,7 @@ static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) /* open.c */ extern int fsverity_file_open(struct inode *inode, struct file *filp); +extern int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); extern void fsverity_cleanup_inode(struct inode *inode); #else /* !CONFIG_FS_VERITY */
@@ -62,6 +63,12 @@ static inline int fsverity_file_open(struct inode *inode, struct file *filp) return IS_VERITY(inode) ? -EOPNOTSUPP : 0; } +static inline int fsverity_prepare_setattr(struct dentry *dentry, + struct iattr *attr) +{ + return IS_VERITY(d_inode(dentry)) ? -EOPNOTSUPP : 0; +} + static inline void fsverity_cleanup_inode(struct inode *inode) { }
--
2.22.0