From patchwork Fri Nov 17 17:21:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mikulas Patocka X-Patchwork-Id: 13459171 X-Patchwork-Delegate: snitzer@redhat.com Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A62E3064B for ; Fri, 17 Nov 2023 17:21:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WjCNoQTu" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700241677; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/svBxIG5pwZVgNOLV2M1jD8LhDYxTwLlFhJEi66yFmE=; b=WjCNoQTudlSwuAGviWKbq+rdeUsYXObKClkwsruj4Pdnam2mec+dn4N1x6w6VNQ+JenCRM y8plz46WvQ0lq+QgQDdzZR4hfRLv07dFP2rkRQ191EJ7OP5OaqXtCFbVGIj5ME+CtyWzz+ e/4KoboMNGCOWCpw5lsh+eA5GBlLW0w= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-659-NfJvQNPYPvChRG5L-Z7lNQ-1; Fri, 17 Nov 2023 12:21:14 -0500 X-MC-Unique: NfJvQNPYPvChRG5L-Z7lNQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4DDBD1C07550; Fri, 17 Nov 2023 17:21:14 +0000 (UTC) Received: from file1-rdu.file-001.prod.rdu2.dc.redhat.com (unknown [10.11.5.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4838B492BFD; Fri, 17 Nov 2023 17:21:14 +0000 (UTC) Received: by file1-rdu.file-001.prod.rdu2.dc.redhat.com (Postfix, from userid 12668) id 4028B30C1A8C; Fri, 17 Nov 2023 17:21:14 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by file1-rdu.file-001.prod.rdu2.dc.redhat.com (Postfix) with ESMTP id 3F6CE3FB76; Fri, 17 Nov 2023 18:21:14 +0100 (CET) Date: Fri, 17 Nov 2023 18:21:14 +0100 (CET) From: Mikulas Patocka To: Mike Snitzer cc: Christian Loehle , Harshit Mogalapalli , Heinz Mauelshagen , dm-devel@lists.linux.dev Subject: [PATCH 1/3] dm-delay: fix a race between delay_presuspend and delay_bio In-Reply-To: <1b597cf-499b-a84c-fa5a-87a630987dff@redhat.com> Message-ID: <59bf73d6-bee6-b734-b030-6872fea5b8d@redhat.com> References: <1b597cf-499b-a84c-fa5a-87a630987dff@redhat.com> Precedence: bulk X-Mailing-List: dm-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com In delay_presuspend, we set the atomic variable may_delay and then stop the timer and flush pending bios. The intention here is to prevent the delay target from re-arming the timer again. However, this test is racy. Suppose that one thread goes to delay_bio, sees that dc->may_delay is one and proceeds; now, another theread executes delay_presuspend, it sets, dc->may_delay to zero, deletes the timer and flushes pending bios. Now, the first thread continues and adds the bio to delayed->list despite the fact that dc->may_delay is false. In order to fix this bug, we change may_delay's type from atomic_t to bool and we read and write it only while holding the delayed_bios_lock mutex. Note that we don't have to grab the mutex in delay_resume because there are no bios in flight at this point. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org --- drivers/md/dm-delay.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) Index: linux-2.6/drivers/md/dm-delay.c =================================================================== --- linux-2.6.orig/drivers/md/dm-delay.c 2023-11-17 14:31:29.000000000 +0100 +++ linux-2.6/drivers/md/dm-delay.c 2023-11-17 14:55:10.000000000 +0100 @@ -33,7 +33,7 @@ struct delay_c { struct work_struct flush_expired_bios; struct list_head delayed_bios; struct task_struct *worker; - atomic_t may_delay; + bool may_delay; struct delay_class read; struct delay_class write; @@ -236,7 +236,7 @@ static int delay_ctr(struct dm_target *t ti->private = dc; INIT_LIST_HEAD(&dc->delayed_bios); - atomic_set(&dc->may_delay, 1); + dc->may_delay = true; dc->argc = argc; ret = delay_class_ctr(ti, &dc->read, argv); @@ -312,7 +312,7 @@ static int delay_bio(struct delay_c *dc, struct dm_delay_info *delayed; unsigned long expires = 0; - if (!c->delay || !atomic_read(&dc->may_delay)) + if (!c->delay) return DM_MAPIO_REMAPPED; delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info)); @@ -321,6 +321,10 @@ static int delay_bio(struct delay_c *dc, delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay); mutex_lock(&delayed_bios_lock); + if (unlikely(!dc->may_delay)) { + mutex_unlock(&delayed_bios_lock); + return DM_MAPIO_REMAPPED; + } c->ops++; list_add_tail(&delayed->list, &dc->delayed_bios); mutex_unlock(&delayed_bios_lock); @@ -337,7 +341,9 @@ static void delay_presuspend(struct dm_t { struct delay_c *dc = ti->private; - atomic_set(&dc->may_delay, 0); + mutex_lock(&delayed_bios_lock); + dc->may_delay = false; + mutex_unlock(&delayed_bios_lock); if (delay_is_fast(dc)) flush_delayed_bios_fast(dc, true); @@ -351,7 +357,7 @@ static void delay_resume(struct dm_targe { struct delay_c *dc = ti->private; - atomic_set(&dc->may_delay, 1); + dc->may_delay = true; } static int delay_map(struct dm_target *ti, struct bio *bio)