[PATCH 01/13] fs: add FS_XFLAG_VERITY for verity files

Darrick J. Wong
2024-03-30T00:32:56Z

From: Andrey Albershteyn <aalbersh@redhat.com>

Add extended attribute FS_XFLAG_VERITY for inodes with fs-verity
enabled.

Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
[djwong: fix broken verity flag checks]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
Documentation/filesystems/fsverity.rst | 8 ++++++++
fs/ioctl.c | 11 +++++++++++
include/uapi/linux/fs.h | 1 +
3 files changed, 20 insertions(+)

diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
index 13e4b18e5dbbb..887cdaf162a99 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -326,6 +326,14 @@ the file has fs-verity enabled. This can perform better than
FS_IOC_GETFLAGS and FS_IOC_MEASURE_VERITY because it doesn't require
opening the file, and opening verity files can be expensive.

+FS_IOC_FSGETXATTR
+-----------------
+
+Since Linux v6.9, the FS_IOC_FSGETXATTR ioctl sets FS_XFLAG_VERITY (0x00020000)
+in the returned flags when the file has verity enabled. Note that this attribute
+cannot be set with FS_IOC_FSSETXATTR as enabling verity requires input
+parameters. See FS_IOC_ENABLE_VERITY.
+
.. _accessing_verity_files:

Accessing verity files
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 1d5abfdf0f22a..8b5d842b8ee12 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -481,6 +481,8 @@ void fileattr_fill_xflags(struct fileattr *fa, u32 xflags)
fa->flags |= FS_DAX_FL;
if (fa->fsx_xflags & FS_XFLAG_PROJINHERIT)
fa->flags |= FS_PROJINHERIT_FL;
+ if (fa->fsx_xflags & FS_XFLAG_VERITY)
+ fa->flags |= FS_VERITY_FL;
}
EXPORT_SYMBOL(fileattr_fill_xflags);

@@ -511,6 +513,8 @@ void fileattr_fill_flags(struct fileattr *fa, u32 flags)
fa->fsx_xflags |= FS_XFLAG_DAX;
if (fa->flags & FS_PROJINHERIT_FL)
fa->fsx_xflags |= FS_XFLAG_PROJINHERIT;
+ if (fa->flags & FS_VERITY_FL)
+ fa->fsx_xflags |= FS_XFLAG_VERITY;
}
EXPORT_SYMBOL(fileattr_fill_flags);

@@ -641,6 +645,13 @@ static int fileattr_set_prepare(struct inode *inode,
!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
return -EINVAL;

+ /*
+ * Verity cannot be changed through FS_IOC_FSSETXATTR/FS_IOC_SETFLAGS.
+ * See FS_IOC_ENABLE_VERITY.
+ */
+ if ((fa->fsx_xflags ^ old_ma->fsx_xflags) & FS_XFLAG_VERITY)
+ return -EINVAL;
+
/* Extent size hints of zero turn off the flags. */
if (fa->fsx_extsize == 0)
fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT);
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 45e4e64fd6643..101d1d71242c7 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -158,6 +158,7 @@ struct fsxattr {
#define FS_XFLAG_FILESTREAM 0x00004000 /* use filestream allocator */
#define FS_XFLAG_DAX 0x00008000 /* use DAX for IO */
#define FS_XFLAG_COWEXTSIZE 0x00010000 /* CoW extent size allocator hint */
+#define FS_XFLAG_VERITY 0x00020000 /* fs-verity enabled */
#define FS_XFLAG_HASATTR 0x80000000 /* no DIFLAG for this */

/* the read-only stuff doesn't really belong here, but any other place is