From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:47490 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729543AbeKZWAb (ORCPT ); Mon, 26 Nov 2018 17:00:31 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ilya Dryomov Subject: [PATCH 4.19 117/118] libceph: fall back to sendmsg for slab pages Date: Mon, 26 Nov 2018 11:51:51 +0100 Message-Id: <20181126105106.496968704@linuxfoundation.org> In-Reply-To: <20181126105059.832485122@linuxfoundation.org> References: <20181126105059.832485122@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ilya Dryomov commit 7e241f647dc7087a0401418a187f3f5b527cc690 upstream. skb_can_coalesce() allows coalescing neighboring slab objects into a single frag: return page == skb_frag_page(frag) && off == frag->page_offset + skb_frag_size(frag); ceph_tcp_sendpage() can be handed slab pages. One example of this is XFS: it passes down sector sized slab objects for its metadata I/O. If the kernel client is co-located on the OSD node, the skb may go through loopback and pop on the receive side with the exact same set of frags. When tcp_recvmsg() attempts to copy out such a frag, hardened usercopy complains because the size exceeds the object's allocated size: usercopy: kernel memory exposure attempt detected from ffff9ba917f20a00 (kmalloc-512) (1024 bytes) Although skb_can_coalesce() could be taught to return false if the resulting frag would cross a slab object boundary, we already have a fallback for non-refcounted pages. Utilize it for slab pages too. Cc: stable@vger.kernel.org # 4.8+ Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman --- net/ceph/messenger.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -593,9 +593,15 @@ static int ceph_tcp_sendpage(struct sock struct bio_vec bvec; int ret; - /* sendpage cannot properly handle pages with page_count == 0, - * we need to fallback to sendmsg if that's the case */ - if (page_count(page) >= 1) + /* + * sendpage cannot properly handle pages with page_count == 0, + * we need to fall back to sendmsg if that's the case. + * + * Same goes for slab pages: skb_can_coalesce() allows + * coalescing neighboring slab objects into a single frag which + * triggers one of hardened usercopy checks. + */ + if (page_count(page) >= 1 && !PageSlab(page)) return __ceph_tcp_sendpage(sock, page, offset, size, more); bvec.bv_page = page;