From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:36166 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967624AbeE1KQC (ORCPT ); Mon, 28 May 2018 06:16:02 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Gustavo A. R. Silva" , Andrew Morton , Alexei Starovoitov , Dan Williams , Thomas Gleixner , Peter Zijlstra , Linus Torvalds Subject: [PATCH 4.4 014/268] kernel/sys.c: fix potential Spectre v1 issue Date: Mon, 28 May 2018 11:59:48 +0200 Message-Id: <20180528100203.711487090@linuxfoundation.org> In-Reply-To: <20180528100202.045206534@linuxfoundation.org> References: <20180528100202.045206534@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gustavo A. R. Silva commit 23d6aef74da86a33fa6bb75f79565e0a16ee97c2 upstream. `resource' can be controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: kernel/sys.c:1474 __do_compat_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap) kernel/sys.c:1455 __do_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap) Fix this by sanitizing *resource* before using it to index current->signal->rlim Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Link: http://lkml.kernel.org/r/20180515030038.GA11822@embeddedor.com Signed-off-by: Gustavo A. R. Silva Reviewed-by: Andrew Morton Cc: Alexei Starovoitov Cc: Dan Williams Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/sys.c | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/sys.c +++ b/kernel/sys.c @@ -53,6 +53,8 @@ #include #include +#include + #include /* Move somewhere else to avoid recompiling? */ #include @@ -1311,6 +1313,7 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned if (resource >= RLIM_NLIMITS) return -EINVAL; + resource = array_index_nospec(resource, RLIM_NLIMITS); task_lock(current->group_leader); x = current->signal->rlim[resource]; task_unlock(current->group_leader);