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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 00B7CC433B4 for ; Tue, 4 May 2021 10:16:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C96C161164 for ; Tue, 4 May 2021 10:16:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229947AbhEDKQ4 (ORCPT ); Tue, 4 May 2021 06:16:56 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2991 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230205AbhEDKQz (ORCPT ); Tue, 4 May 2021 06:16:55 -0400 Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FZFns1XS9z6xhY7; Tue, 4 May 2021 18:05:05 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 4 May 2021 12:15:58 +0200 Received: from [10.47.95.108] (10.47.95.108) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Tue, 4 May 2021 11:15:58 +0100 Subject: Re: [PATCH V4 0/4] blk-mq: fix request UAF related with iterating over tagset requests To: Ming Lei , Jens Axboe CC: , Bart Van Assche , Khazhy Kumykov , Shin'ichiro Kawasaki , Hannes Reinecke , David Jeffery References: <20210429023458.3044317-1-ming.lei@redhat.com> From: John Garry Message-ID: Date: Tue, 4 May 2021 11:15:37 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20210429023458.3044317-1-ming.lei@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.95.108] X-ClientProxiedBy: lhreml708-chm.china.huawei.com (10.201.108.57) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 29/04/2021 03:34, Ming Lei wrote: > Hi Jens, > > This patchset fixes the request UAF issue by one simple approach, > without clearing ->rqs[] in fast path. > > 1) grab request's ref before calling ->fn in blk_mq_tagset_busy_iter, > and release it after calling ->fn, so ->fn won't be called for one > request if its queue is frozen, done in 2st patch > > 2) clearing any stale request referred in ->rqs[] before freeing the > request pool, one per-tags spinlock is added for protecting > grabbing request ref vs. clearing ->rqs[tag], so UAF by refcount_inc_not_zero > in bt_tags_iter() is avoided, done in 3rd patch. > I had a go at testing this. Without any modifications for testing, it looks ok. However I also tested by adding an artificial delay in bt_iter() - otherwise it may not be realistic to trigger some UAF issues in sane timeframes. So I made this change: --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -215,8 +215,11 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) * We can hit rq == NULL here, because the tagging functions * test and set the bit before assigning ->rqs[]. */ - if (rq && rq->q == hctx->queue && rq->mq_hctx == hctx) - return iter_data->fn(hctx, rq, iter_data->data, reserved); + if (rq) { + mdelay(50); + if (rq->q == hctx->queue && rq->mq_hctx == hctx) + return iter_data->fn(hctx, rq, iter_data->data, reserved); + } return true; } And I could trigger this pretty quickly: [ 129.318623] ================================================================== [ 129.325870] BUG: KASAN: use-after-free in bt_iter+0xa0/0x120 [ 129.331548] Read of size 8 at addr ffff0010cc62a200 by task fio/1610 [ 129.339384] CPU: 33 PID: 1610 Comm: fio Not tainted 5.12.0-rc4-47861-g2edb78df2141 #1140 [ 129.339395] Hardware name: Huawei Taishan 2280 /D05, BIOS Hisilicon D05 IT21 Nemo 2.0 RC0 04/18/2018 [ 129.339403] Call trace: [ 129.339408] dump_backtrace+0x0/0x2d0 [ 129.339430] show_stack+0x18/0x68 [ 129.339441] dump_stack+0x100/0x16c [ 129.339455] print_address_description.constprop.13+0x68/0x30c [ 129.339468] kasan_report+0x1d8/0x240 [ 129.339479] __asan_load8+0x9c/0xd8 [ 129.339488] bt_iter+0xa0/0x120 [ 129.339496] blk_mq_queue_tag_busy_iter+0x2d8/0x540 [ 129.339506] blk_mq_in_flight+0x80/0xb8 [ 129.339516] part_stat_show+0xcc/0x210 [ 129.339528] dev_attr_show+0x44/0x90 [ 129.339542] sysfs_kf_seq_show+0x128/0x1c8 [ 129.339554] kernfs_seq_show+0xa0/0xb8 [ 129.339563] seq_read_iter+0x210/0x660 [ 129.339575] kernfs_fop_read_iter+0x208/0x2b0 [ 129.339585] new_sync_read+0x1ec/0x2d0 [ 129.339596] vfs_read+0x188/0x248 [ 129.339605] ksys_read+0xc8/0x178 [ 129.339615] __arm64_sys_read+0x44/0x58 [ 129.339625] el0_svc_common.constprop.1+0xc4/0x190 [ 129.339639] do_el0_svc+0x90/0xa0 [ 129.339648] el0_svc+0x24/0x38 [ 129.339659] el0_sync_handler+0x90/0xb8 [ 129.339670] el0_sync+0x154/0x180 [ 129.341162] Allocated by task 1613: [ 129.344644] stack_trace_save+0x94/0xc8 [ 129.344662] kasan_save_stack+0x28/0x58 [ 129.344670] __kasan_slab_alloc+0x88/0xa8 [ 129.344679] slab_post_alloc_hook+0x58/0x2a0 [ 129.344691] kmem_cache_alloc+0x19c/0x2c0 [ 129.344699] io_submit_one+0x138/0x1580 [ 129.344710] __arm64_sys_io_submit+0x120/0x310 [ 129.344721] el0_svc_common.constprop.1+0xc4/0x190 [ 129.344731] do_el0_svc+0x90/0xa0 [ 129.344741] el0_svc+0x24/0x38 [ 129.344750] el0_sync_handler+0x90/0xb8 [ 129.344760] el0_sync+0x154/0x180 [ 129.346250] Freed by task 496: [ 129.349297] stack_trace_save+0x94/0xc8 [ 129.349307] kasan_save_stack+0x28/0x58 [ 129.349315] kasan_set_track+0x28/0x40 [ 129.349323] kasan_set_free_info+0x28/0x50 [ 129.349332] __kasan_slab_free+0xd0/0x130 [ 129.349340] slab_free_freelist_hook+0x70/0x178 [ 129.349352] kmem_cache_free+0x94/0x400 [ 129.349359] aio_complete_rw+0x4f8/0x7f8 [ 129.349369] blkdev_bio_end_io+0xe0/0x1e8 [ 129.349380] bio_endio+0x1d4/0x1f0 [ 129.349392] blk_update_request+0x388/0x6b8 [ 129.349401] scsi_end_request+0x54/0x320 [ 129.349411] scsi_io_completion+0xec/0x700 [ 129.349420] scsi_finish_command+0x168/0x1e8 [ 129.349432] scsi_softirq_done+0x140/0x1b8 [ 129.349441] blk_mq_complete_request+0x4c/0x60 [ 129.349449] scsi_mq_done+0x68/0x88 [ 129.349457] sas_scsi_task_done+0xe0/0x118 [ 129.349470] slot_complete_v2_hw+0x23c/0x620 [ 129.349483] cq_thread_v2_hw+0x10c/0x388 [ 129.349493] irq_thread_fn+0x48/0xd8 [ 129.349503] irq_thread+0x1d4/0x2f8 [ 129.349511] kthread+0x224/0x230 [ 129.349521] ret_from_fork+0x10/0x30 [ 129.351012] The buggy address belongs to the object at ffff0010cc62a200 which belongs to the cache aio_kiocb of size 176 [ 129.363351] The buggy address is located 0 bytes inside of 176-byte region [ffff0010cc62a200, ffff0010cc62a2b0) [ 129.374909] The buggy address belongs to the page: [ 129.379693] page:0000000026f8d4c3 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10cc62a [ 129.379704] head:0000000026f8d4c3 order:1 compound_mapcount:0 [ 129.379710] flags: 0xbfffc0000010200(slab|head) [ 129.379727] raw: 0bfffc0000010200 dead000000000100 dead000000000122 ffff04100630f780 [ 129.379736] raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000 [ 129.379742] page dumped because: kasan: bad access detected [ 129.381229] Memory state around the buggy address: [ 129.386012] ffff0010cc62a100: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 129.393228] ffff0010cc62a180: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc [ 129.400443] >ffff0010cc62a200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 129.407657] ^ [ 129.410878] ffff0010cc62a280: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc [ 129.418092] ffff0010cc62a300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 129.425306] ================================================================== [ 129.432520] Disabling lock debugging due to kernel taint root@ubuntu:/home/john# My script simply kicks off fio running some data on the disk on which / is mounted, and then continually changes IO sched from none->mq-deadline->none for that same disk. I have not had a chance to try to identify the issue. I would also have added a delay in bt_tags_iter() for testing also, but since I got a UAF, above, I didn't try that yet. Thanks, John