4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Frank Sorenson sorenson@redhat.com
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
--- net/sunrpc/xdr.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
--- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -639,11 +639,10 @@ void xdr_truncate_encode(struct xdr_stre 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;