From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759848AbcCDQLh (ORCPT ); Fri, 4 Mar 2016 11:11:37 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:60643 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759570AbcCDQC5 (ORCPT ); Fri, 4 Mar 2016 11:02:57 -0500 Message-Id: <20160304153001.365998400@1wt.eu> User-Agent: quilt/0.63-1 Date: Fri, 04 Mar 2016 16:30:15 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ben Hutchings , Willy Tarreau Subject: [PATCH 2.6.32 15/55] pipe: Fix buffer offset after partially failed read MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 In-Reply-To: <148ee355b419e9976ca727513a1405c8@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Ben Hutchings Quoting the RHEL advisory: > It was found that the fix for CVE-2015-1805 incorrectly kept buffer > offset and buffer length in sync on a failed atomic read, potentially > resulting in a pipe buffer state corruption. A local, unprivileged user > could use this flaw to crash the system or leak kernel memory to user > space. (CVE-2016-0774, Moderate) The same flawed fix was applied to stable branches from 2.6.32.y to 3.14.y inclusive, and I was able to reproduce the issue on 3.2.y. We need to give pipe_iov_copy_to_user() a separate offset variable and only update the buffer offset if it succeeds. References: https://rhn.redhat.com/errata/RHSA-2016-0103.html Signed-off-by: Ben Hutchings Signed-off-by: Willy Tarreau --- fs/pipe.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/pipe.c b/fs/pipe.c index daa71ea..d34cce9 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -360,6 +360,7 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov, void *addr; size_t chars = buf->len, remaining; int error, atomic; + int offset; if (chars > total_len) chars = total_len; @@ -373,9 +374,10 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov, atomic = !iov_fault_in_pages_write(iov, chars); remaining = chars; + offset = buf->offset; redo: addr = ops->map(pipe, buf, atomic); - error = pipe_iov_copy_to_user(iov, addr, &buf->offset, + error = pipe_iov_copy_to_user(iov, addr, &offset, &remaining, atomic); ops->unmap(pipe, buf, addr); if (unlikely(error)) { @@ -391,6 +393,7 @@ redo: break; } ret += chars; + buf->offset += chars; buf->len -= chars; if (!buf->len) { buf->ops = NULL; -- 1.7.12.2.21.g234cd45.dirty