ovl: Handle verity during copy-up

During regular metacopy, if lowerdata file has fs-verity enabled, and
the verity option is enabled, we add the digest to the metacopy xattr.

If verity is required, and lowerdata does not have fs-verity enabled,
fall back to full copy-up (or the generated metacopy would not
validate).

Signed-off-by: Alexander Larsson <alexl@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

1 files changed, 44 insertions, 4 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 68f01fd7f211..2ead7c9a7748 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -544,6 +544,7 @@ struct ovl_copy_up_ctx {
 	bool origin;
 	bool indexed;
 	bool metacopy;
+	bool metacopy_digest;
 };
 
 static int ovl_link_up(struct ovl_copy_up_ctx *c)
@@ -641,8 +642,20 @@ static int ovl_copy_up_metadata(struct ovl_copy_up_ctx *c, struct dentry *temp)
 	}
 
 	if (c->metacopy) {
-		err = ovl_check_setxattr(ofs, temp, OVL_XATTR_METACOPY,
-					 NULL, 0, -EOPNOTSUPP);
+		struct path lowerdatapath;
+		struct ovl_metacopy metacopy_data = OVL_METACOPY_INIT;
+
+		ovl_path_lowerdata(c->dentry, &lowerdatapath);
+		if (WARN_ON_ONCE(lowerdatapath.dentry == NULL))
+			return -EIO;
+		err = ovl_get_verity_digest(ofs, &lowerdatapath, &metacopy_data);
+		if (err)
+			return err;
+
+		if (metacopy_data.digest_algo)
+			c->metacopy_digest = true;
+
+		err = ovl_set_metacopy_xattr(ofs, temp, &metacopy_data);
 		if (err)
 			return err;
 	}
@@ -751,9 +764,15 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
 	if (err)
 		goto cleanup;
 
-	if (!c->metacopy)
-		ovl_set_upperdata(d_inode(c->dentry));
 	inode = d_inode(c->dentry);
+	if (c->metacopy_digest)
+		ovl_set_flag(OVL_HAS_DIGEST, inode);
+	else
+		ovl_clear_flag(OVL_HAS_DIGEST, inode);
+	ovl_clear_flag(OVL_VERIFIED_DIGEST, inode);
+
+	if (!c->metacopy)
+		ovl_set_upperdata(inode);
 	ovl_inode_update(inode, temp);
 	if (S_ISDIR(inode->i_mode))
 		ovl_set_flag(OVL_WHITEOUTS, inode);
@@ -813,6 +832,12 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c)
 	if (err)
 		goto out_fput;
 
+	if (c->metacopy_digest)
+		ovl_set_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
+	else
+		ovl_clear_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
+	ovl_clear_flag(OVL_VERIFIED_DIGEST, d_inode(c->dentry));
+
 	if (!c->metacopy)
 		ovl_set_upperdata(d_inode(c->dentry));
 	ovl_inode_update(d_inode(c->dentry), dget(temp));
@@ -918,6 +943,19 @@ static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
 	if (flags && ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC)))
 		return false;
 
+	/* Fall back to full copy if no fsverity on source data and we require verity */
+	if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
+		struct path lowerdata;
+
+		ovl_path_lowerdata(dentry, &lowerdata);
+
+		if (WARN_ON_ONCE(lowerdata.dentry == NULL) ||
+		    ovl_ensure_verity_loaded(&lowerdata) ||
+		    !fsverity_active(d_inode(lowerdata.dentry))) {
+			return false;
+		}
+	}
+
 	return true;
 }
 
@@ -984,6 +1022,8 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
 	if (err)
 		goto out_free;
 
+	ovl_clear_flag(OVL_HAS_DIGEST, d_inode(c->dentry));
+	ovl_clear_flag(OVL_VERIFIED_DIGEST, d_inode(c->dentry));
 	ovl_set_upperdata(d_inode(c->dentry));
 out_free:
 	kfree(capability);