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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 21160ECE58E for ; Thu, 17 Oct 2019 14:08:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E8F412054F for ; Thu, 17 Oct 2019 14:08:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730605AbfJQOI1 (ORCPT ); Thu, 17 Oct 2019 10:08:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34690 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727429AbfJQOI1 (ORCPT ); Thu, 17 Oct 2019 10:08:27 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DA6C630842A9; Thu, 17 Oct 2019 14:08:26 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D08765D6C8; Thu, 17 Oct 2019 14:08:26 +0000 (UTC) Received: from zmail25.collab.prod.int.phx2.redhat.com (zmail25.collab.prod.int.phx2.redhat.com [10.5.83.31]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id C534A4EE50; Thu, 17 Oct 2019 14:08:26 +0000 (UTC) Date: Thu, 17 Oct 2019 10:08:26 -0400 (EDT) From: Ronnie Sahlberg To: Pavel Shilovsky , linux-cifs Cc: Frank Sorenson , David Wysochanski Message-ID: <1383472639.7033868.1571321306723.JavaMail.zimbra@redhat.com> In-Reply-To: References: <1206360169.6955748.1571271438699.JavaMail.zimbra@redhat.com> <1205168.6984242.1571303132895.JavaMail.zimbra@redhat.com> Subject: Re: list_del corruption while iterating retry_list in cifs_reconnect still seen on 5.4-rc3 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.64.54.116, 10.4.195.29] Thread-Topic: list_del corruption while iterating retry_list in cifs_reconnect still seen on 5.4-rc3 Thread-Index: +EwffHQSmzXHqV9xGX6r/Hquw40nZg== X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Thu, 17 Oct 2019 14:08:26 +0000 (UTC) Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org List, Pavel, So I think there are two bugs we need to fix in this small block to make it safe against a race against other threads calling cifs_delete_mid() and similar. We need to to protect the list mutate functions and wrap them inside the GlobalMid_Lock mutex but we can not hold this lock across the callback call. But we still need to protect the mid_entry dereference and the ->callback call against the mid structure being freed by DeleteMidQEntry(). We can do that by taking out an extra reference to the mid while holding the GlobalMid_Lock and then dropping the reference again after the callback completes. I think something like this might work : diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index bdea4b3e8005..3a1a9b63bd9b 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -572,11 +572,19 @@ cifs_reconnect(struct TCP_Server_Info *server) mutex_unlock(&server->srv_mutex); cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__); + spin_lock(&GlobalMid_Lock); list_for_each_safe(tmp, tmp2, &retry_list) { mid_entry = list_entry(tmp, struct mid_q_entry, qhead); list_del_init(&mid_entry->qhead); + kref_get(&mid_entry->refcount); + spin_unlock(&GlobalMid_Lock); + mid_entry->callback(mid_entry); + cifs_mid_q_entry_release(mid_entry); + + spin_lock(&GlobalMid_Lock); } + spin_unlock(&GlobalMid_Lock); if (cifs_rdma_enabled(server)) { mutex_lock(&server->srv_mutex); Pavel, can you have a look at this and comment? It is very delicate code so it needs careful review. regards ronnie sahlberg ----- Original Message ----- From: "David Wysochanski" To: "Ronnie Sahlberg" Cc: "linux-cifs" , "Frank Sorenson" Sent: Thursday, 17 October, 2019 9:42:08 PM Subject: Re: list_del corruption while iterating retry_list in cifs_reconnect still seen on 5.4-rc3 On Thu, Oct 17, 2019 at 5:05 AM Ronnie Sahlberg wrote: > > > > > > 575--> list_for_each_safe(tmp, tmp2, &retry_list) { > > > 576 mid_entry = list_entry(tmp, struct mid_q_entry, qhead); > > > 577 list_del_init(&mid_entry->qhead); > > > 578 mid_entry->callback(mid_entry); > > > 579 } > > This part (and a similar loop during shutting down the demultiplex thread) is the only place > where we add/remove to the ->qhead list without holding the GlobalMid_Lock. > > I wonder if it is racing against a different thread also modifying qhead for the same mid, > like cifs_delete_mid() for example. > Yes I agree, I was thinking along these same lines of reasoning as I read the code. I put the latest on the investigation into the bug: https://bugzilla.redhat.com/show_bug.cgi?id=1654538#c15 Just before the crash, when we hit the iteration of retry_list something has gone wrong - the very first mid_entry on retry_list is a garbage address, when normally it should be the last address from the previous call to list_move in the loop above it. ----- Original Message ----- > > From: "Ronnie Sahlberg" > > To: "David Wysochanski" > > Cc: "linux-cifs" , "Frank Sorenson" > > Sent: Thursday, 17 October, 2019 10:17:18 AM > > Subject: Re: list_del corruption while iterating retry_list in cifs_reconnect still seen on 5.4-rc3 > > > > I can not reproduce this :-( > > > > I have run it for a few hours, restarting samba in a loop with up to 30 > > threads. > > I am not sure if it helps but I have 8 CPUs on my VM. I also have server signing and client signing mandatory. I can send you the smb.conf offline. > > > > Can you check > > 1, If this only reproduce for you for the root of the share or it also > > reproduces for a subdirectory? > > 2, Does it reproduce also if you use "nohandlecache" mount option? > > This disables the use of cached open of the root handle, i.e. > > open_shroot() > > 3, When this happens, can you check the content of the mid entry and what > > these fields are: > > mid->mid_flags, mid->handle (this is a function pointer, what does it > > point to) > > mid->command. Maybe print the whole structure. > > Ok I'll see what I can find out. So far I am not sure I have identified what else is touching the mid in between the two loops. > > regards > > ronnie sahlberg > > > > > > > > > > ----- Original Message ----- > > > From: "David Wysochanski" > > > To: "linux-cifs" > > > Cc: "Frank Sorenson" > > > Sent: Thursday, 17 October, 2019 5:27:02 AM > > > Subject: list_del corruption while iterating retry_list in cifs_reconnect > > > still seen on 5.4-rc3 > > > > > > I think this has been there for a long time, since we first saw this > > > on a 4.18.0 based kernel but I just noticed the bug recently. > > > I just retested on 5.4-rc3 and it's still there. Easy to repro with a > > > fairly simple but invasive server restart test - takes only maybe a > > > couple minutes on my VM. > > > > > > > > > From Frank Sorenson: > > > > > > mount off a samba server: > > > > > > # mount //vm1/share /mnt/vm1 > > > -overs=2.1,hard,sec=ntlmssp,credentials=/root/.smb_creds > > > > > > > > > on the client, start 10 'find' loops: > > > > > > # export test_path=/mnt/vm1 > > > # do_find() { while true ; do find $test_path >/dev/null 2>&1 ; done } > > > > > > # for i in {1..10} ; do do_find & done > > > > > > > > > optional: also start something to monitor for when the hang occurs: > > > > > > # while true ; do count=$(grep smb2_reconnect /proc/*/stack -A3 | > > > grep -c open_shroot) ; [[ $count -gt 0 ]] && { echo "$(date): > > > reproduced bug" ; break ; } ; echo "$(date): stayin' alive" ; sleep 2 > > > ; done > > > > > > > > > > > > On the samba server: restart smb.service (loop it in case it requires > > > more than one restart): > > > > > > # while true ; do echo "$(date): restarting" ; systemctl restart > > > smb.service ; sleep 5 ; done | tee /var/tmp/smb_restart_log.out > > > > > > > > > > > > > > > [ 430.454897] list_del corruption. prev->next should be > > > ffff98d3a8f316c0, but was 2e885cb266355469 > > > [ 430.464668] ------------[ cut here ]------------ > > > [ 430.466569] kernel BUG at lib/list_debug.c:51! > > > [ 430.468476] invalid opcode: 0000 [#1] SMP PTI > > > [ 430.470286] CPU: 0 PID: 13267 Comm: cifsd Kdump: loaded Not tainted > > > 5.4.0-rc3+ #19 > > > [ 430.473472] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 > > > [ 430.475872] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55 > > > [ 430.478129] Code: 5e 15 8e e8 54 a3 c5 ff 0f 0b 48 c7 c7 78 5f 15 > > > 8e e8 46 a3 c5 ff 0f 0b 48 89 f2 48 89 fe 48 c7 c7 38 5f 15 8e e8 32 > > > a3 c5 ff <0f> 0b 48 89 fe 4c 89 c2 48 c7 c7 00 5f 15 8e e8 1e a3 c5 ff > > > 0f 0b > > > [ 430.485563] RSP: 0018:ffffb4db0042fd38 EFLAGS: 00010246 > > > [ 430.487665] RAX: 0000000000000054 RBX: ffff98d3aabb8800 RCX: > > > 0000000000000000 > > > [ 430.490513] RDX: 0000000000000000 RSI: ffff98d3b7a17908 RDI: > > > ffff98d3b7a17908 > > > [ 430.493383] RBP: ffff98d3a8f316c0 R08: ffff98d3b7a17908 R09: > > > 0000000000000285 > > > [ 430.496258] R10: ffffb4db0042fbf0 R11: ffffb4db0042fbf5 R12: > > > ffff98d3aabb89c0 > > > [ 430.499113] R13: ffffb4db0042fd48 R14: 2e885cb266355469 R15: > > > ffff98d3b24c4480 > > > [ 430.501981] FS: 0000000000000000(0000) GS:ffff98d3b7a00000(0000) > > > knlGS:0000000000000000 > > > [ 430.505232] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > [ 430.507546] CR2: 00007f08cd17b9c0 CR3: 000000023484a000 CR4: > > > 00000000000406f0 > > > [ 430.510426] Call Trace: > > > [ 430.511500] cifs_reconnect+0x25e/0x610 [cifs] > > > [ 430.513350] cifs_readv_from_socket+0x220/0x250 [cifs] > > > [ 430.515464] cifs_read_from_socket+0x4a/0x70 [cifs] > > > [ 430.517452] ? try_to_wake_up+0x212/0x650 > > > [ 430.519122] ? cifs_small_buf_get+0x16/0x30 [cifs] > > > [ 430.521086] ? allocate_buffers+0x66/0x120 [cifs] > > > [ 430.523019] cifs_demultiplex_thread+0xdc/0xc30 [cifs] > > > [ 430.525116] kthread+0xfb/0x130 > > > [ 430.526421] ? cifs_handle_standard+0x190/0x190 [cifs] > > > [ 430.528514] ? kthread_park+0x90/0x90 > > > [ 430.530019] ret_from_fork+0x35/0x40 > > > [ 430.531487] Modules linked in: cifs libdes libarc4 ip6t_rpfilter > > > ip6t_REJECT nf_reject_ipv6 xt_conntrack ebtable_nat ip6table_nat > > > ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat > > > iptable_mangle iptable_raw iptable_security nf_conntrack > > > nf_defrag_ipv6 nf_defrag_ipv4 ip_set nfnetlink ebtable_filter ebtables > > > ip6table_filter ip6_tables crct10dif_pclmul crc32_pclmul joydev > > > virtio_balloon ghash_clmulni_intel i2c_piix4 nfsd nfs_acl lockd > > > auth_rpcgss grace sunrpc xfs libcrc32c virtio_net net_failover > > > crc32c_intel virtio_console serio_raw virtio_blk ata_generic failover > > > pata_acpi qemu_fw_cfg > > > [ 430.552782] ---[ end trace c91d4468f8689482 ]--- > > > [ 430.554948] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55 > > > [ 430.557251] Code: 5e 15 8e e8 54 a3 c5 ff 0f 0b 48 c7 c7 78 5f 15 > > > 8e e8 46 a3 c5 ff 0f 0b 48 89 f2 48 89 fe 48 c7 c7 38 5f 15 8e e8 32 > > > a3 c5 ff <0f> 0b 48 89 fe 4c 89 c2 48 c7 c7 00 5f 15 8e e8 1e a3 c5 ff > > > 0f 0b > > > [ 430.565019] RSP: 0018:ffffb4db0042fd38 EFLAGS: 00010246 > > > [ 430.567181] RAX: 0000000000000054 RBX: ffff98d3aabb8800 RCX: > > > 0000000000000000 > > > [ 430.570073] RDX: 0000000000000000 RSI: ffff98d3b7a17908 RDI: > > > ffff98d3b7a17908 > > > [ 430.572955] RBP: ffff98d3a8f316c0 R08: ffff98d3b7a17908 R09: > > > 0000000000000285 > > > [ 430.575854] R10: ffffb4db0042fbf0 R11: ffffb4db0042fbf5 R12: > > > ffff98d3aabb89c0 > > > [ 430.578745] R13: ffffb4db0042fd48 R14: 2e885cb266355469 R15: > > > ffff98d3b24c4480 > > > [ 430.581624] FS: 0000000000000000(0000) GS:ffff98d3b7a00000(0000) > > > knlGS:0000000000000000 > > > [ 430.584881] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > [ 430.587230] CR2: 00007f08cd17b9c0 CR3: 000000023484a000 CR4: > > > 00000000000406f0 > > > > > > > > > crash> dis -lr cifs_reconnect+0x25e | tail --lines=20 > > > 0xffffffffc062dc26 : movb > > > $0x0,0xbb36b(%rip) # 0xffffffffc06e8f98 > > > /mnt/build/kernel/fs/cifs/connect.c: 572 > > > 0xffffffffc062dc2d : mov %r12,%rdi > > > 0xffffffffc062dc30 : callq > > > 0xffffffff8d9d5a20 > > > /mnt/build/kernel/fs/cifs/connect.c: 574 > > > 0xffffffffc062dc35 : testb > > > $0x1,0xbb300(%rip) # 0xffffffffc06e8f3c > > > 0xffffffffc062dc3c : je > > > 0xffffffffc062dc43 > > > /mnt/build/kernel/./arch/x86/include/asm/jump_label.h: 25 > > > 0xffffffffc062dc3e : data32 data32 data32 > > > xchg %ax,%ax > > > /mnt/build/kernel/fs/cifs/connect.c: 575 > > > 0xffffffffc062dc43 : mov 0x8(%rsp),%rbp > > > 0xffffffffc062dc48 : mov 0x0(%rbp),%r14 > > > 0xffffffffc062dc4c : cmp %r13,%rbp > > > 0xffffffffc062dc4f : jne > > > 0xffffffffc062dc56 > > > 0xffffffffc062dc51 : jmp > > > 0xffffffffc062dc90 > > > 0xffffffffc062dc53 : mov %rax,%r14 > > > /mnt/build/kernel/./include/linux/list.h: 190 > > > 0xffffffffc062dc56 : mov %rbp,%rdi > > > 0xffffffffc062dc59 : callq > > > 0xffffffff8d4e6b00 <__list_del_entry_valid> > > > 0xffffffffc062dc5e : test %al,%al > > > > > > > > > fs/cifs/connect.c > > > 566 mid_entry = list_entry(tmp, struct mid_q_entry, qhead); > > > 567 if (mid_entry->mid_state == MID_REQUEST_SUBMITTED) > > > 568 mid_entry->mid_state = MID_RETRY_NEEDED; > > > 569 list_move(&mid_entry->qhead, &retry_list); > > > 570 } > > > 571 spin_unlock(&GlobalMid_Lock); > > > 572 mutex_unlock(&server->srv_mutex); > > > 573 > > > 574 cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__); > > > 575--> list_for_each_safe(tmp, tmp2, &retry_list) { > > > 576 mid_entry = list_entry(tmp, struct mid_q_entry, qhead); > > > 577 list_del_init(&mid_entry->qhead); > > > 578 mid_entry->callback(mid_entry); > > > 579 } > > > 580 > > > 581 if (cifs_rdma_enabled(server)) { > > > 582 mutex_lock(&server->srv_mutex); > > > 583 smbd_destroy(server); > > > 584 mutex_unlock(&server->srv_mutex); > > > > > -- Dave Wysochanski Principal Software Maintenance Engineer T: 919-754-4024