From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755466AbeDCLnF (ORCPT ); Tue, 3 Apr 2018 07:43:05 -0400 Received: from mail-he1eur01on0136.outbound.protection.outlook.com ([104.47.0.136]:23317 "EHLO EUR01-HE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755135AbeDCLnD (ORCPT ); Tue, 3 Apr 2018 07:43:03 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=ktkhai@virtuozzo.com; Subject: Re: possible deadlock in skb_queue_tail To: Dmitry Vyukov , Ingo Molnar Cc: syzbot , David Miller , David Herrmann , Denys Vlasenko , David Windsor , elena.reshetova@intel.com, ishkamiel@gmail.com, Kees Cook , LKML , matthew@mjdsystems.ca, Mateusz Jurczyk , netdev , syzkaller-bugs@googlegroups.com, Al Viro , xemul@virtuozzo.com References: <0000000000003584570568da18dd@google.com> <06c79d3f-3f28-7f1e-9431-66c18149c9e6@virtuozzo.com> From: Kirill Tkhai 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1;HE1PR0801MB1338;7:HqCxj61CV4auitjhjLp7JVLX17qssFDqNK3x13/w1chsdweRNrsJaBbOob5Wp7mBQ9kbydNE6qSUpJScDJV29e0htrm3346rs+DzJq9wmFuKcwpVPwEOFPI/g3QP8tVpICujfWuT78KSgma5civ5zHzpf8PYF40ScnDkXXpYzEawNvznnSFCQv/WqqqQlu24uaeScz7S5AGterpLjzNyRvnM7lhJAeLT3GrU+kUit0EBgKauY3lkE8ifncaK1dyj;20:YRyzIC4jM2vUslp85eummGusR7/ZiZC0SgsEamckUJP59acfHEpxbin5bZ3viskAe+Z0HWdZWvg6bsN8bGtY8KQoO4G92XjguboJnBsVj0aurlvN9Tp1vghLulmJE65SfGiEtf8aU2Rna0+m62a+UerKCpohL9aAqwwCBEjnCI4= X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Apr 2018 11:42:56.5592 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 46ac9ea0-5960-4020-76af-08d599580b81 X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0801MB1338 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03.04.2018 14:25, Dmitry Vyukov wrote: > On Tue, Apr 3, 2018 at 11:50 AM, Kirill Tkhai wrote: >> On 02.04.2018 12:20, syzbot wrote: >>> Hello, >>> >>> syzbot hit the following crash on net-next commit >>> 06b19fe9a6df7aaa423cd8404ebe5ac9ec4b2960 (Sun Apr 1 03:37:33 2018 +0000) >>> Merge branch 'chelsio-inline-tls' >>> syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=6b495100f17ca8554ab9 >>> >>> Unfortunately, I don't have any reproducer for this crash yet. >>> Raw console output: https://syzkaller.appspot.com/x/log.txt?id=6218830443446272 >>> Kernel config: https://syzkaller.appspot.com/x/.config?id=3327544840960562528 >>> compiler: gcc (GCC) 7.1.1 20170620 >>> >>> IMPORTANT: if you fix the bug, please add the following tag to the commit: >>> Reported-by: syzbot+6b495100f17ca8554ab9@syzkaller.appspotmail.com >>> It will help syzbot understand when the bug is fixed. See footer for details. >>> If you forward the report, please keep this part and the footer. >>> >>> >>> ====================================================== >>> WARNING: possible circular locking dependency detected >>> 4.16.0-rc6+ #290 Not tainted >>> ------------------------------------------------------ >>> syz-executor7/20971 is trying to acquire lock: >>> (&af_unix_sk_receive_queue_lock_key){+.+.}, at: [<00000000271ef0d8>] skb_queue_tail+0x26/0x150 net/core/skbuff.c:2899 >>> >>> but task is already holding lock: >>> (&(&u->lock)->rlock/1){+.+.}, at: [<000000004e725e14>] unix_state_double_lock+0x7b/0xb0 net/unix/af_unix.c:1088 >>> >>> which lock already depends on the new lock. >>> >>> >>> the existing dependency chain (in reverse order) is: >>> >>> -> #1 (&(&u->lock)->rlock/1){+.+.}: >>> _raw_spin_lock_nested+0x28/0x40 kernel/locking/spinlock.c:354 >>> sk_diag_dump_icons net/unix/diag.c:82 [inline] >>> sk_diag_fill.isra.4+0xa52/0xfe0 net/unix/diag.c:144 >>> sk_diag_dump net/unix/diag.c:178 [inline] >>> unix_diag_dump+0x400/0x4f0 net/unix/diag.c:206 >>> netlink_dump+0x492/0xcf0 net/netlink/af_netlink.c:2221 >>> __netlink_dump_start+0x4ec/0x710 net/netlink/af_netlink.c:2318 >>> netlink_dump_start include/linux/netlink.h:214 [inline] >>> unix_diag_handler_dump+0x3e7/0x750 net/unix/diag.c:307 >>> __sock_diag_cmd net/core/sock_diag.c:230 [inline] >>> sock_diag_rcv_msg+0x204/0x360 net/core/sock_diag.c:261 >>> netlink_rcv_skb+0x14b/0x380 net/netlink/af_netlink.c:2443 >>> sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:272 >>> netlink_unicast_kernel net/netlink/af_netlink.c:1307 [inline] >>> netlink_unicast+0x4c4/0x6b0 net/netlink/af_netlink.c:1333 >>> netlink_sendmsg+0xa4a/0xe80 net/netlink/af_netlink.c:1896 >>> sock_sendmsg_nosec net/socket.c:629 [inline] >>> sock_sendmsg+0xca/0x110 net/socket.c:639 >>> sock_write_iter+0x31a/0x5d0 net/socket.c:908 >>> call_write_iter include/linux/fs.h:1782 [inline] >>> new_sync_write fs/read_write.c:469 [inline] >>> __vfs_write+0x684/0x970 fs/read_write.c:482 >>> vfs_write+0x189/0x510 fs/read_write.c:544 >>> SYSC_write fs/read_write.c:589 [inline] >>> SyS_write+0xef/0x220 fs/read_write.c:581 >>> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 >>> entry_SYSCALL_64_after_hwframe+0x42/0xb7 >>> >>> -> #0 (&af_unix_sk_receive_queue_lock_key){+.+.}: >>> lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920 >>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] >>> _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152 >>> skb_queue_tail+0x26/0x150 net/core/skbuff.c:2899 >>> unix_dgram_sendmsg+0xa30/0x1610 net/unix/af_unix.c:1807 >>> sock_sendmsg_nosec net/socket.c:629 [inline] >>> sock_sendmsg+0xca/0x110 net/socket.c:639 >>> ___sys_sendmsg+0x320/0x8b0 net/socket.c:2047 >>> __sys_sendmmsg+0x1ee/0x620 net/socket.c:2137 >>> SYSC_sendmmsg net/socket.c:2168 [inline] >>> SyS_sendmmsg+0x35/0x60 net/socket.c:2163 >>> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 >>> entry_SYSCALL_64_after_hwframe+0x42/0xb7 >> >> sk_diag_dump_icons() dumps only sockets in TCP_LISTEN state. >> TCP_LISTEN state may be assigned in only place in net/unix/af_unix.c: >> it's unix_listen(). The function is applied to stream and seqpacket >> socket types. >> >> It can't be stream because of the second stack, and seqpacket also can't, >> as I don't think it's possible for gcc to inline unix_seqpacket_sendmsg() >> in the way, we don't see it in the stack. >> >> So, this is looks like false positive result for me. >> >> Kirill > > Do you mean that these &(&u->lock)->rlock/1 referenced in 2 stacks are > always different? In these 2 particular stacks they have to be different. But we may meet another stacks, where stream or seqpacket functions are used instead of unix_dgram_sendmsg(), and they may be true positive. Kirill > +Ingo for lockdep false positive > Do we need some kind of annotation here? > > >>> other info that might help us debug this: >>> >>> Possible unsafe locking scenario: >>> >>> CPU0 CPU1 >>> ---- ---- >>> lock(&(&u->lock)->rlock/1); >>> lock(&af_unix_sk_receive_queue_lock_key); >>> lock(&(&u->lock)->rlock/1); >>> lock(&af_unix_sk_receive_queue_lock_key); >>> >>> *** DEADLOCK *** >>> >>> 1 lock held by syz-executor7/20971: >>> #0: (&(&u->lock)->rlock/1){+.+.}, at: [<000000004e725e14>] unix_state_double_lock+0x7b/0xb0 net/unix/af_unix.c:1088 >>> >>> stack backtrace: >>> CPU: 0 PID: 20971 Comm: syz-executor7 Not tainted 4.16.0-rc6+ #290 >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >>> Call Trace: >>> __dump_stack lib/dump_stack.c:17 [inline] >>> dump_stack+0x194/0x24d lib/dump_stack.c:53 >>> print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223 >>> check_prev_add kernel/locking/lockdep.c:1863 [inline] >>> check_prevs_add kernel/locking/lockdep.c:1976 [inline] >>> validate_chain kernel/locking/lockdep.c:2417 [inline] >>> __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3431 >>> lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920 >>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] >>> _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152 >>> skb_queue_tail+0x26/0x150 net/core/skbuff.c:2899 >>> unix_dgram_sendmsg+0xa30/0x1610 net/unix/af_unix.c:1807 >>> sock_sendmsg_nosec net/socket.c:629 [inline] >>> sock_sendmsg+0xca/0x110 net/socket.c:639 >>> ___sys_sendmsg+0x320/0x8b0 net/socket.c:2047 >>> __sys_sendmmsg+0x1ee/0x620 net/socket.c:2137 >>> SYSC_sendmmsg net/socket.c:2168 [inline] >>> SyS_sendmmsg+0x35/0x60 net/socket.c:2163 >>> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 >>> entry_SYSCALL_64_after_hwframe+0x42/0xb7 >>> RIP: 0033:0x455269 >>> RSP: 002b:00007f71ffad6c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 >>> RAX: ffffffffffffffda RBX: 00007f71ffad76d4 RCX: 0000000000455269 >>> RDX: 04924924924924f4 RSI: 0000000020000200 RDI: 0000000000000016 >>> RBP: 000000000072bf58 R08: 0000000000000000 R09: 0000000000000000 >>> R10: 00000000200000d4 R11: 0000000000000246 R12: 00000000ffffffff >>> R13: 00000000000004ca R14: 00000000006f9390 R15: 0000000000000001 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: sync thread started: state = BACKUP, mcast_ifn = bcsh0, syncid = 0, id = 0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> IPVS: Unknown mcast interface: bcsh0 >>> >>> >>> --- >>> This bug is generated by a dumb bot. It may contain errors. >>> See https://goo.gl/tpsmEJ for details. >>> Direct all questions to syzkaller@googlegroups.com. >>> >>> syzbot will keep track of this bug report. >>> If you forgot to add the Reported-by tag, once the fix for this bug is merged >>> into any tree, please reply to this email with: >>> #syz fix: exact-commit-title >>> To mark this as a duplicate of another syzbot report, please reply with: >>> #syz dup: exact-subject-of-another-report >>> If it's a one-off invalid bug report, please reply with: >>> #syz invalid >>> Note: if the crash happens again, it will cause creation of a new bug report. >>> Note: all commands must start from beginning of the line in the email body. >> >> -- >> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. >> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com. >> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/06c79d3f-3f28-7f1e-9431-66c18149c9e6%40virtuozzo.com. >> For more options, visit https://groups.google.com/d/optout.