From: J. Bruce Fields Date: Mon, 11 Jan 2021 21:01:29 +0000 (-0500) Subject: nfsd4: readdirplus shouldn't return parent of export X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=51b2ee7d006a736a9126e8111d1f24e4fd0afaa6;p=linux.git nfsd4: readdirplus shouldn't return parent of export If you export a subdirectory of a filesystem, a READDIRPLUS on the root of that export will return the filehandle of the parent with the ".." entry. The filehandle is optional, so let's just not return the filehandle for ".." if we're at the root of an export. Note that once the client learns one filehandle outside of the export, they can trivially access the rest of the export using further lookups. However, it is also not very difficult to guess filehandles outside of the export. So exporting a subdirectory of a filesystem should considered equivalent to providing access to the entire filesystem. To avoid confusion, we recommend only exporting entire filesystems. Reported-by: Youjipeng Signed-off-by: J. Bruce Fields Cc: stable@vger.kernel.org Signed-off-by: Chuck Lever --- diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c index 821db21ba072c..34b880211e5ea 100644 --- a/fs/nfsd/nfs3xdr.c +++ b/fs/nfsd/nfs3xdr.c @@ -865,9 +865,14 @@ compose_entry_fh(struct nfsd3_readdirres *cd, struct svc_fh *fhp, if (isdotent(name, namlen)) { if (namlen == 2) { dchild = dget_parent(dparent); - /* filesystem root - cannot return filehandle for ".." */ + /* + * Don't return filehandle for ".." if we're at + * the filesystem or export root: + */ if (dchild == dparent) goto out; + if (dparent == exp->ex_path.dentry) + goto out; } else dchild = dget(dparent); } else