From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752523AbcFEK6r (ORCPT ); Sun, 5 Jun 2016 06:58:47 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:21606 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750863AbcFEKU5 (ORCPT ); Sun, 5 Jun 2016 06:20:57 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ben Hutchings , Willy Tarreau Subject: [PATCH 3.10 001/143] pipe: Fix buffer offset after partially failed read Date: Sun, 5 Jun 2016 12:18:24 +0200 Message-Id: <1465122046-9645-2-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1465122046-9645-1-git-send-email-w@1wt.eu> References: <1465122046-9645-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 3e7ab27..50267e6 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -401,6 +401,7 @@ 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; @@ -414,9 +415,10 @@ 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)) { @@ -432,6 +434,7 @@ redo: break; } ret += chars; + buf->offset += chars; buf->len -= chars; /* Was it a packet buffer? Clean up and exit */ -- 2.8.0.rc2.1.gbe9624a