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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 12EEDC76188 for ; Fri, 19 Jul 2019 04:02:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC1CF218A6 for ; Fri, 19 Jul 2019 04:02:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563508957; bh=jcUkRjwMhQ/ORG8sZHca2w3d73uThSyyH5niWnxwa2Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HQHi4Liuf9BvEra43mmAv8owNSb11fkSTksu/JAJjoECfJIaFkfshoHWA1oscdAR/ 5jH5DfJKj6oT/grQjS6hM/lrJni6PeD38sFhakX7MgrvxMBaheQMHPulKvjdqs4RGG ENecf4/RReyxG9XvDYOjvmJ6SFKtJV7oMe7gR2Xs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727035AbfGSECg (ORCPT ); Fri, 19 Jul 2019 00:02:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:34502 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730074AbfGSECd (ORCPT ); Fri, 19 Jul 2019 00:02:33 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 841E021852; Fri, 19 Jul 2019 04:02:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563508953; bh=jcUkRjwMhQ/ORG8sZHca2w3d73uThSyyH5niWnxwa2Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ew44vIQZSxDbfCGU+ruk3+waCnyK239Uipco9VjE/OAaa8MvLBM1IOi3urtHlUsId yoUMHC7gNt+rrJ3jUvQg7gxuSk6fc+RFpPBPhumy4XSuuqCObrTQkrS7j6nh18XcI3 rL0zQvJDE8IRkCcByvFgWaJZVz1WqvIwNs+eXw38= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Konstantin Khlebnikov , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Oleg Nesterov , Michal Hocko , Alexey Dobriyan , Matthew Wilcox , Cyrill Gorcunov , Kirill Tkhai , Al Viro , Roman Gushchin , Andrew Morton , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 5.2 170/171] mm: use down_read_killable for locking mmap_sem in access_remote_vm Date: Thu, 18 Jul 2019 23:56:41 -0400 Message-Id: <20190719035643.14300-170-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190719035643.14300-1-sashal@kernel.org> References: <20190719035643.14300-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Konstantin Khlebnikov [ Upstream commit 1e426fe28261b03f297992e89da3320b42816f4e ] This function is used by ptrace and proc files like /proc/pid/cmdline and /proc/pid/environ. Access_remote_vm never returns error codes, all errors are ignored and only size of successfully read data is returned. So, if current task was killed we'll simply return 0 (bytes read). Mmap_sem could be locked for a long time or forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation. Link: http://lkml.kernel.org/r/156007494202.3335.16782303099589302087.stgit@buzz Signed-off-by: Konstantin Khlebnikov Reviewed-by: Michal Koutný Acked-by: Oleg Nesterov Acked-by: Michal Hocko Cc: Alexey Dobriyan Cc: Matthew Wilcox Cc: Cyrill Gorcunov Cc: Kirill Tkhai Cc: Al Viro Cc: Roman Gushchin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- 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 ddf20bd0c317..9a4401d21e94 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4349,7 +4349,9 @@ 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 d8c02fbe03b5..b2823519f8cd 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1792,7 +1792,8 @@ 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); -- 2.20.1