[PATCH 6.18 0/2] Forbid truncate of fsverity files on btrfs

[PATCH 6.18 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: 725bd2f3c81d54edccb66fead01d4c0c222e2231
-- 
2.56.0

[PATCH 6.18 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 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

Patch "fs,fsverity: reject size changes on fsverity files in setattr_prepare" has been added to the 6.18-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    fs,fsverity: reject size changes on fsverity files in setattr_prepare

to the 6.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fs-fsverity-reject-size-changes-on-fsverity-files-in-setattr_prepare.patch
and it can be found in the queue-6.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-352117-greg=kroah.com@vger.kernel.org Tue Oct  6 23:38:38 2026
From: Eric Biggers <ebiggers@kernel.org>
Date: Tue,  6 Oct 2026 23:36:04 +0200
Subject: fs,fsverity: reject size changes on fsverity files in setattr_prepare
To: stable@vger.kernel.org
Cc: fsverity@lists.linux.dev, Christoph Hellwig <hch@lst.de>, Jan Kara <jack@suse.cz>, "Darrick J. Wong" <djwong@kernel.org>, Eric Biggers <ebiggers@kernel.org>
Message-ID: <20261006213605.46946-2-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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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(-)

--- a/fs/attr.c
+++ b/fs/attr.c
@@ -169,7 +169,17 @@ int setattr_prepare(struct mnt_idmap *id
 	 * 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;
 	}
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5898,10 +5898,6 @@ int ext4_setattr(struct mnt_idmap *idmap
 	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)
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1123,10 +1123,6 @@ int f2fs_setattr(struct mnt_idmap *idmap
 	if (err)
 		return err;
 
-	err = fsverity_prepare_setattr(dentry, attr);
-	if (err)
-		return err;
-
 	if (unlikely(IS_IMMUTABLE(inode)))
 		return -EPERM;
 
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -384,14 +384,6 @@ int __fsverity_file_open(struct inode *i
 }
 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);
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -179,7 +179,6 @@ int fsverity_get_digest(struct inode *in
 /* 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(s
 	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(str
 	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 */


Patches currently in stable-queue which might be from ebiggers@kernel.org are

queue-6.18/fs-fsverity-reject-size-changes-on-fsverity-files-in-setattr_prepare.patch
queue-6.18/fs-fsverity-remove-check-for-fsverity-being-enabled-in-setattr_prepare.patch
queue-6.18/fsverity-add-dependency-on-64k-or-smaller-pages.patch
queue-6.18/crypto-x86-aes-gcm-fix-always-true-check-for-last-aad-segment.patch

Re: Patch "fs,fsverity: reject size changes on fsverity files in setattr_prepare" has been added to the 6.18-stable tree

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] vfs: verity file truncation bypass when CONFIG_FS_VERITY is disabled
--

commit 750dd8cb058f7ea5d2ca5305006f1c5e63c6eb32
Author: gregkh@linuxfoundation.org <gregkh@linuxfoundation.org>

fs,fsverity: reject size changes on fsverity files in setattr_prepare

This commit centralizes the check to reject truncates of fsverity files
into setattr_prepare() in fs/attr.c. This removes boilerplate code from
individual filesystems and fixes a missing truncation check in btrfs.

Link: https://lore.kernel.org/r/20260128152630.627409-2-hch@lst.de

> diff --git a/fs/attr.c b/fs/attr.c
> index 795f231d00e8e..2c94af08be183 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;

[Severity: High]
Does this logic inadvertently permit truncating verity files when
CONFIG_FS_VERITY is disabled?

Before this patch, filesystems explicitly called fsverity_prepare_setattr().
When CONFIG_FS_VERITY was disabled, the fallback implementation safely returned
-EOPNOTSUPP for any inode with the verity flag set.

By short-circuiting the check here with IS_ENABLED(CONFIG_FS_VERITY), it
appears an unprivileged user with DAC write access could use sys_truncate()
to bypass the check and modify a verity file if the kernel was built without
fsverity support.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/2026100754-drizzle-shape-0a72@gregkh?part=1

[PATCH 6.18 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 2c94af08be18..3f2cce4e4ad1 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

Patch "fs,fsverity: remove check for fsverity being enabled in setattr_prepare()" has been added to the 6.18-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

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

to the 6.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fs-fsverity-remove-check-for-fsverity-being-enabled-in-setattr_prepare.patch
and it can be found in the queue-6.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-352118-greg=kroah.com@vger.kernel.org Tue Oct  6 23:39:37 2026
From: Eric Biggers <ebiggers@kernel.org>
Date: Tue,  6 Oct 2026 23:36:05 +0200
Subject: fs,fsverity: remove check for fsverity being enabled in setattr_prepare()
To: stable@vger.kernel.org
Cc: fsverity@lists.linux.dev, Andrey Albershteyn <aalbersh@kernel.org>, Christoph Hellwig <hch@lst.de>, Eric Biggers <ebiggers@kernel.org>
Message-ID: <20261006213605.46946-3-ebiggers@kernel.org>

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/attr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/attr.c
+++ b/fs/attr.c
@@ -176,7 +176,7 @@ int setattr_prepare(struct mnt_idmap *id
 		 * 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);


Patches currently in stable-queue which might be from ebiggers@kernel.org are

queue-6.18/fs-fsverity-reject-size-changes-on-fsverity-files-in-setattr_prepare.patch
queue-6.18/fs-fsverity-remove-check-for-fsverity-being-enabled-in-setattr_prepare.patch
queue-6.18/fsverity-add-dependency-on-64k-or-smaller-pages.patch
queue-6.18/crypto-x86-aes-gcm-fix-always-true-check-for-last-aad-segment.patch