[PATCH v2 5/5] ovl: don't require "metacopy=on" for "verity"

[Miklos Szeredi <mszeredi@redhat.com>]

Allow the "verity" mount option to be used with "userxattr" data-only
layer(s).

Previous patches made sure that with "userxattr" metacopy only works in the
lower -> data scenario.

In this scenario the lower (metadata) layer must be secured against
tampering, in which case the verity checksums contained in this layer can
ensure integrity of data even in the case of an untrusted data layer.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/overlayfs/params.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index 54468b2b0fba..8ac0997dca13 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -846,8 +846,8 @@ int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
 		config->uuid = OVL_UUID_NULL;
 	}
 
-	/* Resolve verity -> metacopy dependency */
-	if (config->verity_mode && !config->metacopy) {
+	/* Resolve verity -> metacopy dependency (unless used with userxattr) */
+	if (config->verity_mode && !config->metacopy && !config->userxattr) {
 		/* Don't allow explicit specified conflicting combinations */
 		if (set.metacopy) {
 			pr_err("conflicting options: metacopy=off,verity=%s\n",
@@ -945,7 +945,7 @@ int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
 	}
 
 
-	/* Resolve userxattr -> !redirect && !metacopy && !verity dependency */
+	/* Resolve userxattr -> !redirect && !metacopy dependency */
 	if (config->userxattr) {
 		if (set.redirect &&
 		    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
@@ -957,11 +957,6 @@ int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
 			pr_err("conflicting options: userxattr,metacopy=on\n");
 			return -EINVAL;
 		}
-		if (config->verity_mode) {
-			pr_err("conflicting options: userxattr,verity=%s\n",
-			       ovl_verity_mode(config));
-			return -EINVAL;
-		}
 		/*
 		 * Silently disable default setting of redirect and metacopy.
 		 * This shall be the default in the future as well: these
-- 
2.49.0