diff mbox series

[v5,08/16] fs-verity: add the hook for file ->setattr()

Message ID 20190620205043.64350-9-ebiggers@kernel.org (mailing list archive)
State New, archived
Headers show
Series fs-verity: read-only file-based authenticity protection | expand

Commit Message

Eric Biggers June 20, 2019, 8:50 p.m. UTC 
From: Eric Biggers <ebiggers@google.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@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/verity/open.c         | 21 +++++++++++++++++++++
 include/linux/fsverity.h |  7 +++++++
 2 files changed, 28 insertions(+)

Comments

Jaegeuk Kim June 22, 2019, 10:28 p.m. UTC | #1 
On 06/20, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.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@mit.edu>

Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>

> Signed-off-by: Eric Biggers <ebiggers@google.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
diff mbox series

Patch

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)
 {
 }