From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:47006 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936573AbcKQKer (ORCPT ); Thu, 17 Nov 2016 05:34:47 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Kees Cook , Jerome Marchand , Johannes Weiner , "Kirill A. Shutemov" , Vlastimil Babka , Hugh Dickins , Andrew Morton , Linus Torvalds Subject: [PATCH 4.8 07/92] swapfile: fix memory corruption via malformed swapfile Date: Thu, 17 Nov 2016 11:31:40 +0100 Message-Id: <20161117103224.525925172@linuxfoundation.org> In-Reply-To: <20161117103224.218007793@linuxfoundation.org> References: <20161117103224.218007793@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit dd111be69114cc867f8e826284559bfbc1c40e37 upstream. When root activates a swap partition whose header has the wrong endianness, nr_badpages elements of badpages are swabbed before nr_badpages has been checked, leading to a buffer overrun of up to 8GB. This normally is not a security issue because it can only be exploited by root (more specifically, a process with CAP_SYS_ADMIN or the ability to modify a swap file/partition), and such a process can already e.g. modify swapped-out memory of any other userspace process on the system. Link: http://lkml.kernel.org/r/1477949533-2509-1-git-send-email-jann@thejh.net Signed-off-by: Jann Horn Acked-by: Kees Cook Acked-by: Jerome Marchand Acked-by: Johannes Weiner Cc: "Kirill A. Shutemov" Cc: Vlastimil Babka Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/swapfile.c | 2 ++ 1 file changed, 2 insertions(+) --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2218,6 +2218,8 @@ static unsigned long read_swap_header(st swab32s(&swap_header->info.version); swab32s(&swap_header->info.last_page); swab32s(&swap_header->info.nr_badpages); + if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) + return 0; for (i = 0; i < swap_header->info.nr_badpages; i++) swab32s(&swap_header->info.badpages[i]); }