[PATCH RFC 03/29] fs: add FS_XFLAG_VERITY for verity files

[Andrey Albershteyn <aalbersh@redhat.com>]

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>
Signed-off-by: Andrey Albershteyn <aalbersh@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 dacdbc1149e6..33b588c32ed1 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -342,6 +342,14 @@ 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 v6.17, 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 69107a245b4c..6b94da2b93f5 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -480,6 +480,8 @@ 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);
 
@@ -510,6 +512,8 @@ 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);
 
@@ -640,6 +644,13 @@ 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 0098b0ce8ccb..20777ec55f7b 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -167,6 +167,7 @@ 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

-- 
2.50.0