Commit c1d9b584 authored by Eric Biggers's avatar Eric Biggers
Browse files

fs-verity: add the hook for file ->setattr() 



Add a function fsverity_prepare_setattr() which filesystems that support
fs-verity must call to deny truncates of verity files.

Reviewed-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reviewed-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
parent fd2d1acf

fs/verity/open.c

+21 −0
Original line number Diff line number Diff line
@@ -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

 *

include/linux/fsverity.h

+7 −0
Original line number Diff line number Diff line
@@ -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)

{

}