From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752821AbeC3U6e (ORCPT ); Fri, 30 Mar 2018 16:58:34 -0400 Received: from gateway36.websitewelcome.com ([192.185.199.121]:40992 "EHLO gateway36.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752568AbeC3U6c (ORCPT ); Fri, 30 Mar 2018 16:58:32 -0400 Subject: Re: [PATCH] rbd: remove VLA usage To: Ilya Dryomov Cc: Sage Weil , Alex Elder , Jens Axboe , Ceph Development , linux-block , linux-kernel@vger.kernel.org References: <20180330191759.GA18176@embeddedgus> From: "Gustavo A. R. Silva" Message-ID: <0e56a59e-6dbe-a4c9-f761-e7e7d63db297@embeddedor.com> Date: Fri, 30 Mar 2018 15:34:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.145.54.187 X-Source-L: No X-Exim-ID: 1f20jR-000ULn-2R X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.1.67]) [189.145.54.187]:49244 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 7 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/30/2018 03:29 PM, Ilya Dryomov wrote: > On Fri, Mar 30, 2018 at 9:17 PM, Gustavo A. R. Silva > wrote: >> In preparation to enabling -Wvla, remove the use of stack VLA. >> >> In this particular case, variable buf_size is replaced with a constant >> expression that can be computed at preprocessing time. This avoids two >> VLA warnings. Also, as a consequence of the mentioned change, some code >> was slightly refactored. >> >> The use of stack Variable Length Arrays needs to be avoided, as they >> can be a vector for stack exhaustion, which can be both a runtime bug >> or a security flaw. Also, in general, as code evolves it is easy to >> lose track of how big a VLA can get. Thus, we can end up having runtime >> failures that are hard to debug. >> >> Also, fixed as part of the directive to remove all VLAs from >> the kernel: https://lkml.org/lkml/2018/3/7/621 >> >> Signed-off-by: Gustavo A. R. Silva >> --- >> drivers/block/rbd.c | 15 +++++++-------- >> 1 file changed, 7 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c >> index 1e03b04..5133122 100644 >> --- a/drivers/block/rbd.c >> +++ b/drivers/block/rbd.c >> @@ -3091,20 +3091,20 @@ static int __rbd_notify_op_lock(struct rbd_device *rbd_dev, >> { >> struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc; >> struct rbd_client_id cid = rbd_get_cid(rbd_dev); >> - int buf_size = 4 + 8 + 8 + CEPH_ENCODING_START_BLK_LEN; >> - char buf[buf_size]; >> + char buf[4 + 8 + 8 + CEPH_ENCODING_START_BLK_LEN]; >> void *p = buf; >> >> dout("%s rbd_dev %p notify_op %d\n", __func__, rbd_dev, notify_op); >> >> /* encode *LockPayload NotifyMessage (op + ClientId) */ >> - ceph_start_encoding(&p, 2, 1, buf_size - CEPH_ENCODING_START_BLK_LEN); >> + ceph_start_encoding(&p, 2, 1, >> + sizeof(buf) - CEPH_ENCODING_START_BLK_LEN); >> ceph_encode_32(&p, notify_op); >> ceph_encode_64(&p, cid.gid); >> ceph_encode_64(&p, cid.handle); >> >> return ceph_osdc_notify(osdc, &rbd_dev->header_oid, >> - &rbd_dev->header_oloc, buf, buf_size, >> + &rbd_dev->header_oloc, buf, sizeof(buf), >> RBD_NOTIFY_TIMEOUT, preply_pages, preply_len); >> } >> >> @@ -3610,19 +3610,18 @@ static void __rbd_acknowledge_notify(struct rbd_device *rbd_dev, >> u64 notify_id, u64 cookie, s32 *result) >> { >> struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc; >> - int buf_size = 4 + CEPH_ENCODING_START_BLK_LEN; >> - char buf[buf_size]; >> + char buf[4 + CEPH_ENCODING_START_BLK_LEN]; >> + int buf_size = 0; >> int ret; >> >> if (result) { >> void *p = buf; >> >> + buf_size = sizeof(buf); >> /* encode ResponseMessage */ >> ceph_start_encoding(&p, 1, 1, >> buf_size - CEPH_ENCODING_START_BLK_LEN); >> ceph_encode_32(&p, *result); >> - } else { >> - buf_size = 0; >> } >> >> ret = ceph_osdc_notify_ack(osdc, &rbd_dev->header_oid, > > Already fixed: > > https://github.com/ceph/ceph-client/commit/2474e77e75215a3cad3b652d2f55ba5b123cb119 > Oh, that's great. Good to know. :) Thanks -- Gustavo