From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751790AbeEKSeT (ORCPT ); Fri, 11 May 2018 14:34:19 -0400 Received: from mail-ve1eur01on0103.outbound.protection.outlook.com ([104.47.1.103]:21318 "EHLO EUR01-VE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750980AbeEKSeQ (ORCPT ); Fri, 11 May 2018 14:34:16 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=avagin@virtuozzo.com; Date: Fri, 11 May 2018 11:33:59 -0700 From: Andrei Vagin To: syzbot Cc: avagin@openvz.org, davem@davemloft.net, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: possible deadlock in sk_diag_fill Message-ID: <20180511183358.GA1492@outlook.office365.com> References: <000000000000169606056b793179@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: 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linux-kernel@vger.kernel.org On Sat, May 05, 2018 at 10:59:02AM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: c1c07416cdd4 Merge tag 'kbuild-fixes-v4.17' of git://git.k.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=12164c97800000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5a1dc06635c10d27 > dashboard link: https://syzkaller.appspot.com/bug?extid=c1872be62e587eae9669 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > userspace arch: i386 > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+c1872be62e587eae9669@syzkaller.appspotmail.com > > > ====================================================== > WARNING: possible circular locking dependency detected > 4.17.0-rc3+ #59 Not tainted > ------------------------------------------------------ > syz-executor1/25282 is trying to acquire lock: > 000000004fddf743 (&(&u->lock)->rlock/1){+.+.}, at: sk_diag_dump_icons > net/unix/diag.c:82 [inline] > 000000004fddf743 (&(&u->lock)->rlock/1){+.+.}, at: > sk_diag_fill.isra.5+0xa43/0x10d0 net/unix/diag.c:144 > > but task is already holding lock: > 00000000b6895645 (rlock-AF_UNIX){+.+.}, at: spin_lock > include/linux/spinlock.h:310 [inline] > 00000000b6895645 (rlock-AF_UNIX){+.+.}, at: sk_diag_dump_icons > net/unix/diag.c:64 [inline] > 00000000b6895645 (rlock-AF_UNIX){+.+.}, at: sk_diag_fill.isra.5+0x94e/0x10d0 > net/unix/diag.c:144 > > which lock already depends on the new lock. In the code, we have a comment which explains why it is safe to take this lock /* * The state lock is outer for the same sk's * queue lock. With the other's queue locked it's * OK to lock the state. */ unix_state_lock_nested(req); It is a question how to explain this to lockdep. > > > the existing dependency chain (in reverse order) is: > > -> #1 (rlock-AF_UNIX){+.+.}: > __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:2900 > unix_dgram_sendmsg+0xf77/0x1730 net/unix/af_unix.c:1797 > sock_sendmsg_nosec net/socket.c:629 [inline] > sock_sendmsg+0xd5/0x120 net/socket.c:639 > ___sys_sendmsg+0x525/0x940 net/socket.c:2117 > __sys_sendmmsg+0x3bb/0x6f0 net/socket.c:2205 > __compat_sys_sendmmsg net/compat.c:770 [inline] > __do_compat_sys_sendmmsg net/compat.c:777 [inline] > __se_compat_sys_sendmmsg net/compat.c:774 [inline] > __ia32_compat_sys_sendmmsg+0x9f/0x100 net/compat.c:774 > do_syscall_32_irqs_on arch/x86/entry/common.c:323 [inline] > do_fast_syscall_32+0x345/0xf9b arch/x86/entry/common.c:394 > entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 > > -> #0 (&(&u->lock)->rlock/1){+.+.}: > lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 > _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.5+0xa43/0x10d0 net/unix/diag.c:144 > sk_diag_dump net/unix/diag.c:178 [inline] > unix_diag_dump+0x35f/0x550 net/unix/diag.c:206 > netlink_dump+0x507/0xd20 net/netlink/af_netlink.c:2226 > __netlink_dump_start+0x51a/0x780 net/netlink/af_netlink.c:2323 > netlink_dump_start include/linux/netlink.h:214 [inline] > unix_diag_handler_dump+0x3f4/0x7b0 net/unix/diag.c:307 > __sock_diag_cmd net/core/sock_diag.c:230 [inline] > sock_diag_rcv_msg+0x2e0/0x3d0 net/core/sock_diag.c:261 > netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448 > sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:272 > netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline] > netlink_unicast+0x58b/0x740 net/netlink/af_netlink.c:1336 > netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901 > sock_sendmsg_nosec net/socket.c:629 [inline] > sock_sendmsg+0xd5/0x120 net/socket.c:639 > sock_write_iter+0x35a/0x5a0 net/socket.c:908 > call_write_iter include/linux/fs.h:1784 [inline] > new_sync_write fs/read_write.c:474 [inline] > __vfs_write+0x64d/0x960 fs/read_write.c:487 > vfs_write+0x1f8/0x560 fs/read_write.c:549 > ksys_write+0xf9/0x250 fs/read_write.c:598 > __do_sys_write fs/read_write.c:610 [inline] > __se_sys_write fs/read_write.c:607 [inline] > __ia32_sys_write+0x71/0xb0 fs/read_write.c:607 > do_syscall_32_irqs_on arch/x86/entry/common.c:323 [inline] > do_fast_syscall_32+0x345/0xf9b arch/x86/entry/common.c:394 > entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 > > other info that might help us debug this: > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(rlock-AF_UNIX); > lock(&(&u->lock)->rlock/1); > lock(rlock-AF_UNIX); > lock(&(&u->lock)->rlock/1); > > *** DEADLOCK *** > > 5 locks held by syz-executor1/25282: > #0: 000000003919e1bd (sock_diag_mutex){+.+.}, at: sock_diag_rcv+0x1b/0x40 > net/core/sock_diag.c:271 > #1: 000000004f328d3e (sock_diag_table_mutex){+.+.}, at: __sock_diag_cmd > net/core/sock_diag.c:225 [inline] > #1: 000000004f328d3e (sock_diag_table_mutex){+.+.}, at: > sock_diag_rcv_msg+0x169/0x3d0 net/core/sock_diag.c:261 > #2: 000000004cc04dbb (nlk_cb_mutex-SOCK_DIAG){+.+.}, at: > netlink_dump+0x98/0xd20 net/netlink/af_netlink.c:2182 > #3: 00000000accdef41 (unix_table_lock){+.+.}, at: spin_lock > include/linux/spinlock.h:310 [inline] > #3: 00000000accdef41 (unix_table_lock){+.+.}, at: > unix_diag_dump+0x10a/0x550 net/unix/diag.c:192 > #4: 00000000b6895645 (rlock-AF_UNIX){+.+.}, at: spin_lock > include/linux/spinlock.h:310 [inline] > #4: 00000000b6895645 (rlock-AF_UNIX){+.+.}, at: sk_diag_dump_icons > net/unix/diag.c:64 [inline] > #4: 00000000b6895645 (rlock-AF_UNIX){+.+.}, at: > sk_diag_fill.isra.5+0x94e/0x10d0 net/unix/diag.c:144 > > stack backtrace: > CPU: 1 PID: 25282 Comm: syz-executor1 Not tainted 4.17.0-rc3+ #59 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x1b9/0x294 lib/dump_stack.c:113 > print_circular_bug.isra.36.cold.54+0x1bd/0x27d > 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+0x343e/0x5140 kernel/locking/lockdep.c:3431 > lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 > _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.5+0xa43/0x10d0 net/unix/diag.c:144 > sk_diag_dump net/unix/diag.c:178 [inline] > unix_diag_dump+0x35f/0x550 net/unix/diag.c:206 > netlink_dump+0x507/0xd20 net/netlink/af_netlink.c:2226 > __netlink_dump_start+0x51a/0x780 net/netlink/af_netlink.c:2323 > netlink_dump_start include/linux/netlink.h:214 [inline] > unix_diag_handler_dump+0x3f4/0x7b0 net/unix/diag.c:307 > __sock_diag_cmd net/core/sock_diag.c:230 [inline] > sock_diag_rcv_msg+0x2e0/0x3d0 net/core/sock_diag.c:261 > netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448 > sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:272 > netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline] > netlink_unicast+0x58b/0x740 net/netlink/af_netlink.c:1336 > netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901 > sock_sendmsg_nosec net/socket.c:629 [inline] > sock_sendmsg+0xd5/0x120 net/socket.c:639 > sock_write_iter+0x35a/0x5a0 net/socket.c:908 > call_write_iter include/linux/fs.h:1784 [inline] > new_sync_write fs/read_write.c:474 [inline] > __vfs_write+0x64d/0x960 fs/read_write.c:487 > vfs_write+0x1f8/0x560 fs/read_write.c:549 > ksys_write+0xf9/0x250 fs/read_write.c:598 > __do_sys_write fs/read_write.c:610 [inline] > __se_sys_write fs/read_write.c:607 [inline] > __ia32_sys_write+0x71/0xb0 fs/read_write.c:607 > do_syscall_32_irqs_on arch/x86/entry/common.c:323 [inline] > do_fast_syscall_32+0x345/0xf9b arch/x86/entry/common.c:394 > entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 > RIP: 0023:0xf7f8ccb9 > RSP: 002b:00000000f5f880ac EFLAGS: 00000282 ORIG_RAX: 0000000000000004 > RAX: ffffffffffffffda RBX: 0000000000000017 RCX: 000000002058bfe4 > RDX: 0000000000000029 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > > > --- > This bug is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at 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.