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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 9D604C43381 for ; Wed, 13 Mar 2019 10:25:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5813720449 for ; Wed, 13 Mar 2019 10:25:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726192AbfCMKZN (ORCPT ); Wed, 13 Mar 2019 06:25:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34784 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725847AbfCMKZN (ORCPT ); Wed, 13 Mar 2019 06:25:13 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C93B588AA1; Wed, 13 Mar 2019 10:25:12 +0000 (UTC) Received: from ovpn-200-51.brq.redhat.com (ovpn-200-51.brq.redhat.com [10.40.200.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0180D1001DF9; Wed, 13 Mar 2019 10:25:06 +0000 (UTC) Message-ID: <1552472705.4717.7.camel@redhat.com> Subject: Re: [PATCH] hyper-v: Check for ring buffer in hv_get_bytes_to_read/write From: Mohammed Gamal Reply-To: mgamal@redhat.com To: Haiyang Zhang , Michael Kelley , "linux-hyperv@vger.kernel.org" , kimbrownkd Cc: Sasha Levin , Dexuan Cui , Stephen Hemminger , Long Li , KY Srinivasan , vkuznets , "linux-kernel@vger.kernel.org" Date: Wed, 13 Mar 2019 12:25:05 +0200 In-Reply-To: References: <20190307163606.25212-1-mgamal@redhat.com> <1551983533.5436.8.camel@redhat.com> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Wed, 13 Mar 2019 10:25:12 +0000 (UTC) Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On Tue, 2019-03-12 at 18:02 +0000, Haiyang Zhang wrote: >   >   > > -----Original Message----- > > From: Mohammed Gamal > > Sent: Thursday, March 7, 2019 1:32 PM > > To: Michael Kelley ; linux-hyperv@vger.kern > el.org; > > kimbrownkd > > Cc: Sasha Levin ; Dexuan Cui > > ; Stephen Hemminger ; > > Long Li ; KY Srinivasan ; > Haiyang > > Zhang ; vkuznets ; > linux- > > kernel@vger.kernel.org > > Subject: Re: [PATCH] hyper-v: Check for ring buffer in > > hv_get_bytes_to_read/write > > > > On Thu, 2019-03-07 at 17:33 +0000, Michael Kelley wrote: > > > From: Mohammed Gamal Sent: Thursday, March 7, > > > 2019 8:36 AM > > > > > > > > This patch adds a check for the presence of the ring buffer in > > > > hv_get_bytes_to_read/write() to avoid possible NULL pointer > > > > dereferences. > > > > If the ring buffer is not yet allocated, return 0 bytes to be > > > > read/written. > > > > > > > > The root cause is that code that accesses the ring buffer > including > > > > hv_get_bytes_to_read/write() could be vulnerable to the race > > > > condition discussed in > > > > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F > %2Flk > > > > > > ml.org%2Flkml%2F2018%2F10%2F18%2F779&data=02%7C01%7Chaiyangz > > %40m > > > > > > icrosoft.com%7C73af013c14034bb0b1ad08d6a32b419c%7C72f988bf86f141af9 > > 1 > > > > > > ab2d7cd011db47%7C1%7C0%7C636875803518430021&sdata=b51Xc5GUN > > nHX0K > > > > 08LrH3ShTyFcRZ4mYHUATd%2BDpvYDw%3D&reserved=0>; > > > > > > > > This race is being addressed by the patch series by Kimberly > Brown > > > > in > > > > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F > %2Flk > > > > > > ml.org%2Flkml%2F2019%2F2%2F21%2F1236&data=02%7C01%7Chaiyangz > > %40m > > > > > > icrosoft.com%7C73af013c14034bb0b1ad08d6a32b419c%7C72f988bf86f141af9 > > 1 > > > > > > ab2d7cd011db47%7C1%7C0%7C636875803518430021&sdata=js1ff15Gbk7 > > 0MD > > > > A2hkMZExxvAAbDuKDhfBvc5ZrckzM%3D&reserved=0 which is not > > final > > > > yet > > > > > > > > Signed-off-by: Mohammed Gamal > > > > > > Could you elaborate on the code paths where > > > hv_get_bytes_to_read/write() could be called when the ring buffer > > > isn't yet allocated?  My sense is that Kim Brown's patch will > address > > > all of the code paths that involved sysfs access from outside the > > > driver.  And within a driver, the ring buffer should never be > accessed > > > unless it is already allocated.  Is there another code path we're > not > > > aware of?  I'm wondering if these changes are really needed once > Kim > > > Brown's patch is finished. > > > > > > Michael > > > > I've seen one instance of the race in the netvsc driver when > running traffic > > through it with iperf3 while continuously changing the channel > settings. > > > > The following code path deallocates the ring buffer: > > netvsc_set_channels() -> netvsc_detach() -> > > rndis_filter_device_remove() -> netvsc_device_remove() -> > vmbus_close() > > -> vmbus_free_ring() -> hv_ringbuffer_cleanup(). > > > > netvsc_send_pkt() -> hv_get_bytes_to_write() might get called > concurrently > > after vmbus_close() and before vmbus_open() returns and sets up the > new ring > > buffer. > > > > The race is fairly hard to reproduce on recent upstream kernels, > but I still > > managed to reproduce it. >   > Looking at the code from netvsc_detach() – >          netif_tx_disable(ndev) is called before > rndis_filter_device_remove(hdev, nvdev). > So there should be no call to netvsc_send_pkt() after detaching. > What’s the crash stack trace? >   > static int netvsc_detach(struct net_device *ndev, >                          struct netvsc_device *nvdev) > { >         struct net_device_context *ndev_ctx = netdev_priv(ndev); >         struct hv_device *hdev = ndev_ctx->device_ctx; >         int ret; >   >         /* Don't try continuing to try and setup sub channels */ >         if (cancel_work_sync(&nvdev->subchan_work)) >                 nvdev->num_chn = 1; >   >         /* If device was up (receiving) then shutdown */ >         if (netif_running(ndev)) { >                 netif_tx_disable(ndev); >   >                 ret = rndis_filter_close(nvdev); >                 if (ret) { >                         netdev_err(ndev, >                                    "unable to close device (ret > %d).\n", ret); >                         return ret; >                 } >   >                 ret = netvsc_wait_until_empty(nvdev); >                 if (ret) { >                         netdev_err(ndev, >                                    "Ring buffer not empty after > closing rndis\n"); >                         return ret; >                 } >         } >   >         netif_device_detach(ndev); >   >         rndis_filter_device_remove(hdev, nvdev); >   >         return 0; > } >   > Thanks, > Haiyang Here is one stack trace on a 4.18 kernel, the most recent kernel I managed to reproduce this bug on.  I haven't managed to reproduce on 5.0.0 yet, but I guess some recent changes to the netvsc driver could be masking the problem, as I tried backporting those changes to older RHEL 7 kernels and still managed to reproduce the problem there. I could however be wrong, and any pointers are still appreciated: [  545.308507] BUG: unable to handle kernel NULL pointer dereference at 0000000000000004 [  545.308656] PGD 0 P4D 0  [  545.308763] Oops: 0000 [#1] SMP PTI [  545.308855] CPU: 2 PID: 1800 Comm: iperf3 Kdump: loaded Not tainted 4.18.0-64.el8.test.x86_64 #1 [  545.308990] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v1.0 11/26/2012 [  545.309143] RIP: 0010:netvsc_send+0x2c9/0xce0 [hv_netvsc] [  545.309298] Code: 4c 8b b1 c0 00 00 00 4f 8d 2c 64 49 c1 e5 07 4d 03 ae c0 03 00 00 48 8b 84 03 30 01 00 00 4c 89 6c 24 18 48 8b 90 20 01 00 00 <8b> 72 04 8b 0a 8b 90 38 01 00 00 89 f7 01 f2 29 cf 29 ca 39 ce  0f [  545.309321] RSP: 0018:ffffb8a305d5b6c0 EFLAGS: 00010282 [  545.309321] RAX: ffff926928bd7000 RBX: ffff92687dbe0000 RCX: ffff92687d5bec00 [  545.309321] RDX: 0000000000000000 RSI: ffff92691b61c654 RDI: 0000000000000000 [  545.309321] RBP: ffff926915dcde28 R08: ffff926915dcde00 R09: 0000000000000000 [  545.309321] R10: 00000000000db61c R11: 0000000000000f7e R12: 0000000000000001 [  545.309321] R13: ffff926931808180 R14: ffff926931801000 R15: 0000000000000000 [  545.309321] FS:  00007feca6a4b740(0000) GS:ffff926940080000(0000) knlGS:0000000000000000 [  545.309321] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [  545.309321] CR2: 0000000000000004 CR3: 00000000dfccc004 CR4: 00000000003606e0 [  545.309321] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [  545.309321] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [  545.309321] Call Trace: [  545.309321]  netvsc_start_xmit+0x3c9/0x800 [hv_netvsc] [  545.309321]  ? __switch_to_asm+0x34/0x70 [  545.309321]  ? __switch_to_asm+0x34/0x70 [  545.309321]  ? ___slab_alloc+0x269/0x4e0 [  545.309321]  ? __alloc_skb+0x82/0x1c0 [  545.309321]  ? nft_do_chain+0x3d7/0x3f0 [nf_tables] [  545.309321]  ? nft_do_chain+0x3d7/0x3f0 [nf_tables] [  545.309321]  ? nft_do_chain+0x3d7/0x3f0 [nf_tables] [  545.309321]  ? _cond_resched+0x15/0x30 [  545.309321]  ? netif_skb_features+0x118/0x280 [  545.309321]  dev_hard_start_xmit+0xa5/0x210 [  545.309321]  sch_direct_xmit+0x14f/0x340 [  545.309321]  __dev_queue_xmit+0x799/0x8f0 [  545.309321]  ip_finish_output2+0x2e0/0x430 [  545.309321]  ? ip_finish_output+0x139/0x270 [  545.309321]  ip_output+0x6c/0xe0 [  545.309321]  ? ip_append_data.part.50+0xc0/0xc0 [  545.309321]  ip_send_skb+0x15/0x40 [  545.309321]  udp_send_skb.isra.43+0x153/0x340 [  545.309321]  udp_sendmsg+0xac2/0xd30 [  545.309321]  ? set_fd_set.part.7+0x40/0x40 [  545.309321]  ? set_fd_set.part.7+0x40/0x40 [  545.309321]  ? __check_object_size+0xa3/0x181 [  545.309321]  ? sock_has_perm+0x78/0xa0 [  545.309321]  ? core_sys_select+0x242/0x2f0 [  545.309321]  ? sock_sendmsg+0x36/0x40 [  545.309321]  ? udp_push_pending_frames+0x60/0x60 [  545.309321]  sock_sendmsg+0x36/0x40 [  545.309321]  sock_write_iter+0x8f/0xf0 [  545.309321]  __vfs_write+0x156/0x1a0 [  545.309321]  vfs_write+0xa5/0x1a0 [  545.309321]  ksys_write+0x4f/0xb0 [  545.309321]  do_syscall_64+0x5b/0x1b0 [  545.309321]  entry_SYSCALL_64_after_hwframe+0x65/0xca [  545.309321] RIP: 0033:0x7feca5fb5348 [  545.309321] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 d5 63 2d 00 8b 00 85 c0 75 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 d4 55 [  545.309321] RSP: 002b:00007ffc3ff1f108 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [  545.309321] RAX: ffffffffffffffda RBX: 00000000000005a8 RCX: 00007feca5fb5348 [  545.309321] RDX: 00000000000005a8 RSI: 00007feca6a59000 RDI: 0000000000000009 [  545.309321] RBP: 00007feca6a59000 R08: 0000000000000002 R09: 00cd09a3238b4e43 [  545.309321] R10: 0002961ecea49016 R11: 0000000000000246 R12: 0000000000000009 [  545.309321] R13: 00000000000005a8 R14: 00007ffc3ff1f180 R15: 0000563c1e05b260 [  545.309321] Modules linked in: nft_chain_nat_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 nft_chain_route_ipv6 nft_chain_nat_ipv4 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nft_chain_route_ipv4 nf_conntrack ip_set nf_tables nfnetlink vfat fat sb_edac crct10dif_pclmul crc32_pclmul ghash_clmulni_intel intel_rapl_perf sg hv_utils hv_balloon pcspkr joydev xfs libcrc32c sd_mod sr_mod cdrom serio_raw hv_storvsc hv_netvsc scsi_transport_fc hyperv_fb hyperv_keyboard hid_hyperv crc32c_intel hv_vmbus dm_mirror dm_region_hash dm_log dm_mod [last unloaded: nft_compat] [  545.309321] CR2: 0000000000000004 >From the stack trace netvsc_send+0x2c9 points to this line: static inline u32 hv_get_bytes_to_write(const struct hv_ring_bu ffer_info *rbi) {         u32 read_loc, write_loc, dsize, write;         dsize = rbi->ring_datasize;         read_loc = READ_ONCE(rbi->ring_buffer->read_index); <---------         write_loc = rbi->ring_buffer->write_index;         write = write_loc >= read_loc ? dsize - (write_loc - read_loc)                 read_loc - write_loc;         return write; } which gets called from netvsc_send_pkt().