From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752907AbeDRS4x (ORCPT ); Wed, 18 Apr 2018 14:56:53 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:46730 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750872AbeDRS4w (ORCPT ); Wed, 18 Apr 2018 14:56:52 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07402;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0T.Qn96V_1524077800; From: Yang Shi To: mhocko@kernel.org, gorcunov@gmail.com, akpm@linux-foundation.org Cc: yang.shi@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH -mmotm] prctl: add comment about mmap_sem and arg_lock Date: Thu, 19 Apr 2018 02:56:39 +0800 Message-Id: <1524077799-80690-1-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add comment to elaborate why mmap_sem for is used by prctl. Signed-off-by: Yang Shi --- akpm: this patch can be foled into: mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct.patch kernel/sys.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sys.c b/kernel/sys.c index 0cc5a1c..943fdc5 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2011,6 +2011,10 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data return error; } + /* + * arg_lock protects concurent updates but we still need mmap_sem for + * read to exclude races with sys_brk. + */ down_read(&mm->mmap_sem); /* -- 1.8.3.1