Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753416AbdFGXFi (ORCPT ); Wed, 7 Jun 2017 19:05:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52386 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753398AbdFGXFf (ORCPT ); Wed, 7 Jun 2017 19:05:35 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 23C71804EB Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=mpatocka@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 23C71804EB Date: Wed, 7 Jun 2017 19:05:31 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Shaohua Li , NeilBrown cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra Subject: [PATCH] md: don't use flush_signals in userspace processes Message-ID: User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 07 Jun 2017 23:05:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2356 Lines: 65 The function flush_signals clears all pending signals for the process. It may be used by kernel threads when we need to prepare a kernel thread for responding to signals. However using this function for an userspaces processes is incorrect - clearing signals without the program expecting it can cause misbehavior. The raid1 and raid5 code uses flush_signals in its request routine because it wants to prepare for an interruptible wait. This patch drops flush_signals and uses sigprocmask instead to block all signals (including SIGKILL) around the schedule() call. The signals are not lost, but the schedule() call won't respond to them. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org --- drivers/md/raid1.c | 5 ++++- drivers/md/raid5.c | 5 ++++- 2 files changed, 8 insertions(+), 2 deletions(-) Index: linux-4.12-rc4/drivers/md/raid1.c =================================================================== --- linux-4.12-rc4.orig/drivers/md/raid1.c +++ linux-4.12-rc4/drivers/md/raid1.c @@ -1335,7 +1335,7 @@ static void raid1_write_request(struct m */ DEFINE_WAIT(w); for (;;) { - flush_signals(current); + sigset_t full, old; prepare_to_wait(&conf->wait_barrier, &w, TASK_INTERRUPTIBLE); if (bio_end_sector(bio) <= mddev->suspend_lo || @@ -1345,7 +1345,10 @@ static void raid1_write_request(struct m bio->bi_iter.bi_sector, bio_end_sector(bio)))) break; + sigfillset(&full); + sigprocmask(SIG_BLOCK, &full, &old); schedule(); + sigprocmask(SIG_SETMASK, &old, NULL); } finish_wait(&conf->wait_barrier, &w); } Index: linux-4.12-rc4/drivers/md/raid5.c =================================================================== --- linux-4.12-rc4.orig/drivers/md/raid5.c +++ linux-4.12-rc4/drivers/md/raid5.c @@ -5693,12 +5693,15 @@ static void raid5_make_request(struct md * userspace, we want an interruptible * wait. */ - flush_signals(current); prepare_to_wait(&conf->wait_for_overlap, &w, TASK_INTERRUPTIBLE); if (logical_sector >= mddev->suspend_lo && logical_sector < mddev->suspend_hi) { + sigset_t full, old; + sigfillset(&full); + sigprocmask(SIG_BLOCK, &full, &old); schedule(); + sigprocmask(SIG_SETMASK, &old, NULL); do_prepare = true; } goto retry;