Commit 4293fbc2 authored Oct 30, 2018 by Frank Sorenson Committed by Greg Kroah-Hartman Nov 21, 2018

sunrpc: correct the computation for page_ptr when truncating



commit 5d7a5bcb67c70cbc904057ef52d3fcfeb24420bb upstream.

When truncating the encode buffer, the page_ptr is getting
advanced, causing the next page to be skipped while encoding.
The page is still included in the response, so the response
contains a page of bogus data.

We need to adjust the page_ptr backwards to ensure we encode
the next page into the correct place.

We saw this triggered when concurrent directory modifications caused
nfsd4_encode_direct_fattr() to return nfserr_noent, and the resulting
call to xdr_truncate_encode() corrupted the READDIR reply.

Signed-off-by: Frank Sorenson <sorenson@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent f7e6ee2e

net/sunrpc/xdr.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -639,11 +639,10 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len)
		WARN_ON_ONCE(xdr->iov);
		return;
		}
		if (fraglen) {
		if (fraglen)
		xdr->end = head->iov_base + head->iov_len;
		xdr->page_ptr--;
		}
		/* (otherwise assume xdr->end is already set) */
		xdr->page_ptr--;
		head->iov_len = len;
		buf->len = len;
		xdr->p = head->iov_base + head->iov_len;