[PATCH 6.18 1/2] fs,fsverity: reject size changes on fsverity files in setattr_prepare

[Eric Biggers <ebiggers@kernel.org>]

From: Christoph Hellwig <hch@lst.de>

commit e9734653c523c744f03333ece6ae7a315187f05c upstream.

Add the check to reject truncates of fsverity files directly to
setattr_prepare instead of requiring the file system to handle it.
Besides removing boilerplate code, this also fixes the complete lack of
such check in btrfs.

Fixes: 146054090b08 ("btrfs: initial fsverity support")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Link: https://lore.kernel.org/r/20260128152630.627409-2-hch@lst.de
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 fs/attr.c                | 12 +++++++++++-
 fs/ext4/inode.c          |  4 ----
 fs/f2fs/file.c           |  4 ----
 fs/verity/open.c         |  8 --------
 include/linux/fsverity.h | 25 -------------------------
 5 files changed, 11 insertions(+), 42 deletions(-)

diff --git a/fs/attr.c b/fs/attr.c
index 795f231d00e8..2c94af08be18 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -169,7 +169,17 @@ int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
 	 * ATTR_FORCE.
 	 */
 	if (ia_valid & ATTR_SIZE) {
-		int error = inode_newsize_ok(inode, attr->ia_size);
+		int error;
+
+		/*
+		 * Verity files are immutable, so deny truncates.  This isn't
+		 * covered by the open-time check because sys_truncate() takes a
+		 * path, not an open file.
+		 */
+		if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
+			return -EPERM;
+
+		error = inode_newsize_ok(inode, attr->ia_size);
 		if (error)
 			return error;
 	}
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3b2891f18540..d2977c560c96 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5898,10 +5898,6 @@ int ext4_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	if (error)
 		return error;
 
-	error = fsverity_prepare_setattr(dentry, attr);
-	if (error)
-		return error;
-
 	if (is_quota_modification(idmap, inode, attr)) {
 		error = dquot_initialize(inode);
 		if (error)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 222b2a8bbc94..791f1cf198c1 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1123,10 +1123,6 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	if (err)
 		return err;
 
-	err = fsverity_prepare_setattr(dentry, attr);
-	if (err)
-		return err;
-
 	if (unlikely(IS_IMMUTABLE(inode)))
 		return -EPERM;
 
diff --git a/fs/verity/open.c b/fs/verity/open.c
index 77b1c977af02..2aa5eae5a540 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -384,14 +384,6 @@ int __fsverity_file_open(struct inode *inode, struct file *filp)
 }
 EXPORT_SYMBOL_GPL(__fsverity_file_open);
 
-int __fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr)
-{
-	if (attr->ia_valid & ATTR_SIZE)
-		return -EPERM;
-	return 0;
-}
-EXPORT_SYMBOL_GPL(__fsverity_prepare_setattr);
-
 void __fsverity_cleanup_inode(struct inode *inode)
 {
 	struct fsverity_info **vi_addr = fsverity_info_addr(inode);
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index 5bc7280425a7..86fb1708676b 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -179,7 +179,6 @@ int fsverity_get_digest(struct inode *inode,
 /* 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);
 
 /**
@@ -251,12 +250,6 @@ static inline int __fsverity_file_open(struct inode *inode, struct file *filp)
 	return -EOPNOTSUPP;
 }
 
-static inline int __fsverity_prepare_setattr(struct dentry *dentry,
-					     struct iattr *attr)
-{
-	return -EOPNOTSUPP;
-}
-
 static inline void fsverity_cleanup_inode(struct inode *inode)
 {
 }
@@ -338,22 +331,4 @@ static inline int fsverity_file_open(struct inode *inode, struct file *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 */
-- 
2.56.0