Commit 37b12916 authored Jan 10, 2018 by Amir Goldstein Committed by Miklos Szeredi Jan 24, 2018

ovl: verify stored origin fh matches lower dir



When the NFS export feature is enabled, overlayfs implicitly enables the
feature "verify_lower". When the "verify_lower" feature is enabled, a
directory inode found in lower layer by name or by redirect_dir is
verified against the file handle of the copy up origin that is stored in
the upper layer.

This introduces a change of behavior for the case of lower layer
modification while overlay is offline. A lower directory created or
moved offline under an exisitng upper directory, will not be merged with
that upper directory.

The NFS export feature should not be used after copying layers, because
the new lower directory inodes would fail verification and won't be
merged with upper directories.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

parent f168f109

fs/overlayfs/namei.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -737,6 +737,18 @@ struct dentry ovl_lookup(struct inode dir, struct dentry *dentry,
		}
		}

		/*
		* When "verify_lower" feature is enabled, do not merge with a
		* lower dir that does not match a stored origin xattr.
		*/
		if (upperdentry && !ctr && ovl_verify_lower(dentry->d_sb)) {
		err = ovl_verify_origin(upperdentry, this, false);
		if (err) {
		dput(this);
		break;
		}
		}

		stack[ctr].dentry = this;
		stack[ctr].layer = lower.layer;
		ctr++;

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