From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BA19C04E84 for ; Wed, 15 May 2019 08:21:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4509F20862 for ; Wed, 15 May 2019 08:21:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="fHGe8418" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726039AbfEOIVX (ORCPT ); Wed, 15 May 2019 04:21:23 -0400 Received: from forwardcorp1o.mail.yandex.net ([95.108.205.193]:56004 "EHLO forwardcorp1o.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725871AbfEOIVW (ORCPT ); Wed, 15 May 2019 04:21:22 -0400 Received: from mxbackcorp1o.mail.yandex.net (mxbackcorp1o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::301]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id A784B2E147B; Wed, 15 May 2019 11:21:19 +0300 (MSK) Received: from smtpcorp1p.mail.yandex.net (smtpcorp1p.mail.yandex.net [2a02:6b8:0:1472:2741:0:8b6:10]) by mxbackcorp1o.mail.yandex.net (nwsmtp/Yandex) with ESMTP id DwA5FsojOl-LJ0GRkIN; Wed, 15 May 2019 11:21:19 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1557908479; bh=rH/t30KXMBGr4dF0FJuUrEPHJpTL3NQhSuLj3xwva+0=; h=Message-ID:Date:To:From:Subject; b=fHGe8418tN46yDfQFsQ6wSmHFaUCKDn9hk25OB75c5F8CZaDVuzJE3eqbZhBq6oTD KIU4i3rNGp8X6ahgcORt5JIudN3gzYuTn/Q8xJy2ex/jLMfmHd5kABXrLZg/WNLYXo n7e5PNwGicPSEkyRzqIMK5WMjAeFBYiNWrHhO/lE= Authentication-Results: mxbackcorp1o.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-red.dhcp.yndx.net (dynamic-red.dhcp.yndx.net [2a02:6b8:0:40c:ed19:3833:7ce1:2324]) by smtpcorp1p.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id fxC6AkQBIj-LJd0oVGu; Wed, 15 May 2019 11:21:19 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Subject: [PATCH] mm: use down_read_killable for locking mmap_sem in access_remote_vm From: Konstantin Khlebnikov To: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Oleg Nesterov Date: Wed, 15 May 2019 11:21:18 +0300 Message-ID: <155790847881.2798.7160461383704600177.stgit@buzz> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This function is used by ptrace and proc files like /proc/pid/cmdline and /proc/pid/environ. Return 0 (bytes read) if current task is killed. Mmap_sem could be locked for a long time or forever if something wrong. Signed-off-by: Konstantin Khlebnikov --- mm/memory.c | 4 +++- mm/nommu.c | 3 ++- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 96f1d473c89a..2e6846d09023 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4348,7 +4348,9 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, void *old_buf = buf; int write = gup_flags & FOLL_WRITE; - down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) + return 0; + /* ignore errors, just check how much was successfully transferred */ while (len) { int bytes, ret, offset; diff --git a/mm/nommu.c b/mm/nommu.c index b492fd1fcf9f..cad8fb34088f 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1791,7 +1791,8 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct *vma; int write = gup_flags & FOLL_WRITE; - down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) + return 0; /* the access must start within one of the target process's mappings */ vma = find_vma(mm, addr);