[PATCH 6.12 0/2] Forbid truncate of fsverity files on btrfs

[PATCH 6.12 0/2] Forbid truncate of fsverity files on btrfs

[Eric Biggers]

Backport the fix to forbid truncate(2) of fsverity files on btrfs (and
also the fix for that fix).

Andrey Albershteyn (1):
  fs,fsverity: remove check for fsverity being enabled in
    setattr_prepare()

Christoph Hellwig (1):
  fs,fsverity: reject size changes on fsverity files in setattr_prepare

 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(-)


base-commit: 7aba70ab2e8d8ab3cd45abcaa15e1119a00dc42a
-- 
2.56.0

[PATCH 6.12 1/2] fs,fsverity: reject size changes on fsverity files in setattr_prepare

[Eric Biggers]

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 c04d19b58f12..714f159d58ea 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 fa303effb18a..24b5925a7c7e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5444,10 +5444,6 @@ 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 a7ad5e02433c..b4bd73648a01 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1078,10 +1078,6 @@ 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 fdeb95eca3af..bd0497da5cea 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -392,14 +392,6 @@ 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)
 {
 	fsverity_free_info(inode->i_verity_info);
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index 1eb7eae580be..139a6f5c6217 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -149,7 +149,6 @@ 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);
 
 /**
@@ -214,12 +213,6 @@ 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)
 {
 }
@@ -301,22 +294,4 @@ 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

[PATCH 6.12 2/2] fs,fsverity: remove check for fsverity being enabled in setattr_prepare()

[Eric Biggers]

From: Andrey Albershteyn <aalbersh@kernel.org>

commit d2f96bcb89d36d488a10e3bcf819b98536968286 upstream.

The check that fs-verity is available in the kernel is not necessary
here. Filesystems could have fsverity files even without fs-verity
enabled. In that case, truncate on fsverity file will succeed, what this
check is trying to prevent.

Fixes: e9734653c523 ("fs,fsverity: reject size changes on fsverity files in setattr_prepare")
Cc: stable@vger.kernel.org
Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260727094352.1734826-1-aalbersh@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 fs/attr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/attr.c b/fs/attr.c
index 714f159d58ea..927cb18d25d5 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -176,7 +176,7 @@ int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
 		 * 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))
+		if (IS_VERITY(inode))
 			return -EPERM;
 
 		error = inode_newsize_ok(inode, attr->ia_size);
-- 
2.56.0

Re: [PATCH 6.12 0/2] Forbid truncate of fsverity files on btrfs

[Sasha Levin]

> Backport the fix to forbid truncate(2) of fsverity files on btrfs (and
> also the fix for that fix).

Queued the series for 6.12, thanks.

-- 
Thanks,
Sasha