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Date: Thu, 20 Jun 2019 13:50:35 -0700 From: Eric Biggers <ebiggers@...nel.org> To: linux-fscrypt@...r.kernel.org Cc: linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org, linux-integrity@...r.kernel.org, Jaegeuk Kim <jaegeuk@...nel.org>, "Theodore Y . Ts'o" <tytso@....edu>, Victor Hsieh <victorhsieh@...gle.com>, Chandan Rajendra <chandan@...ux.vnet.ibm.com>, Dave Chinner <david@...morbit.com>, Christoph Hellwig <hch@....de>, "Darrick J . Wong" <darrick.wong@...cle.com>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: [PATCH v5 08/16] fs-verity: add the hook for file ->setattr() From: Eric Biggers <ebiggers@...gle.com> 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@....edu> Signed-off-by: Eric Biggers <ebiggers@...gle.com> --- 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 3a3bb27e23f5e3..21ae0ef254a695 100644 --- a/fs/verity/open.c +++ b/fs/verity/open.c @@ -296,6 +296,27 @@ 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 1372c236c8770c..cbcc358d073652 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) { } -- 2.22.0.410.gd8fdbe21b5-goog
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