Re: possible deadlock in rtnl_lock (2)

[Dmitry Vyukov]

On Sat, Feb 3, 2018 at 12:25 PM, Xin Long <lucien.xin@xxxxxxxxx> wrote:
> On Thu, Feb 1, 2018 at 7:58 PM, syzbot
> <syzbot+61e4972c2b1d5e08a5c2@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> Hello,
>>
>> syzbot hit the following crash on upstream commit
>> 255442c93843f52b6891b21d0b485bf2c97f93c3 (Thu Feb 1 03:25:25 2018 +0000)
>> Merge tag 'docs-4.16' of git://git.lwn.net/linux
>>
>> So far this crash happened 1587 times on net-next, upstream.
>> C reproducer is attached.
>> syzkaller reproducer is attached.
>> Raw console output is attached.
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached.
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+61e4972c2b1d5e08a5c2@xxxxxxxxxxxxxxxxxxxxxxxxx
>> 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
>> 4.15.0+ #290 Not tainted
>> ------------------------------------------------------
>> syzkaller681093/4124 is trying to acquire lock:
>>  (rtnl_mutex){+.+.}, at: [<00000000c3d62391>] rtnl_lock+0x17/0x20
>> net/core/rtnetlink.c:74
>>
>> but task is already holding lock:
>>  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>] lock_sock
>> include/net/sock.h:1461 [inline]
>>  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>] ip_setsockopt+0x8c/0xb0
>> net/ipv4/ip_sockglue.c:1259
>>
>> which lock already depends on the new lock.
>>
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #1 (sk_lock-AF_INET){+.+.}:
>>        lock_sock_nested+0xc2/0x110 net/core/sock.c:2780
>>        lock_sock include/net/sock.h:1461 [inline]
>>        do_ip_getsockopt+0x1b3/0x2170 net/ipv4/ip_sockglue.c:1335
>>        ip_getsockopt+0x90/0x220 net/ipv4/ip_sockglue.c:1566
>>        tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3359
>>        sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2937
>>        SYSC_getsockopt net/socket.c:1880 [inline]
>>        SyS_getsockopt+0x178/0x340 net/socket.c:1862
>>        entry_SYSCALL_64_fastpath+0x29/0xa0
>>
>> -> #0 (rtnl_mutex){+.+.}:
>>        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
>>        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>        __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
>>        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>        rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
>>        register_netdevice_notifier+0xad/0x860 net/core/dev.c:1607
>>        tee_tg_check+0x1a0/0x280 net/netfilter/xt_TEE.c:106
>>        xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:845
>>        check_target net/ipv4/netfilter/ip_tables.c:513 [inline]
>>        find_check_entry.isra.8+0x8c8/0xcb0
>> net/ipv4/netfilter/ip_tables.c:554
>>        translate_table+0xed1/0x1610 net/ipv4/netfilter/ip_tables.c:725
>>        do_replace net/ipv4/netfilter/ip_tables.c:1141 [inline]
>>        do_ipt_set_ctl+0x370/0x5f0 net/ipv4/netfilter/ip_tables.c:1675
>>        nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
>>        nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
>>        ip_setsockopt+0xa1/0xb0 net/ipv4/ip_sockglue.c:1260
>>        sctp_setsockopt+0x2b6/0x61d0 net/sctp/socket.c:4104
>>        sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
>>        SYSC_setsockopt net/socket.c:1849 [inline]
>>        SyS_setsockopt+0x189/0x360 net/socket.c:1828
>>        entry_SYSCALL_64_fastpath+0x29/0xa0
>>
>> other info that might help us debug this:
>>
>>  Possible unsafe locking scenario:
>>
>>        CPU0                    CPU1
>>        ----                    ----
>>   lock(sk_lock-AF_INET);
>>                                lock(rtnl_mutex);
>>                                lock(sk_lock-AF_INET);
>>   lock(rtnl_mutex);
>>
>>  *** DEADLOCK ***
>>
>> 1 lock held by syzkaller681093/4124:
>>  #0:  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>] lock_sock
>> include/net/sock.h:1461 [inline]
>>  #0:  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>]
>> ip_setsockopt+0x8c/0xb0 net/ipv4/ip_sockglue.c:1259
>>
>> stack backtrace:
>> CPU: 0 PID: 4124 Comm: syzkaller681093 Not tainted 4.15.0+ #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+0x194/0x257 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
>>  __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>  __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
>>  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>  rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
>>  register_netdevice_notifier+0xad/0x860 net/core/dev.c:1607
>>  tee_tg_check+0x1a0/0x280 net/netfilter/xt_TEE.c:106
>>  xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:845
>>  check_target net/ipv4/netfilter/ip_tables.c:513 [inline]
>>  find_check_entry.isra.8+0x8c8/0xcb0 net/ipv4/netfilter/ip_tables.c:554
>>  translate_table+0xed1/0x1610 net/ipv4/netfilter/ip_tables.c:725
>>  do_replace net/ipv4/netfilter/ip_tables.c:1141 [inline]
>>  do_ipt_set_ctl+0x370/0x5f0 net/ipv4/netfilter/ip_tables.c:1675
>>  nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
>>  nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
>>  ip_setsockopt+0xa1/0xb0 net/ipv4/ip_sockglue.c:1260
>>  sctp_setsockopt+0x2b6/0x61d0 net/sctp/socket.c:4104
>>  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
>>  SYSC_setsockopt net/socket.c:1849 [inline]
>>  SyS_setsockopt+0x189/0x360 net/socket.c:1828
>>  entry_SYSCALL_64_fastpath+0x29/0xa0
>> RIP: 0033:0x445bd9
>> RSP: 002b:00007fffdfb6a998 EFLAGS: 00000203 ORIG_RAX: 0000000000000036
>> RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000445bd9
>> RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000005
>> RBP: 00007fffdfb6aa48 R08: 0000000000000318 R09: 0000000000000000
>> R10: 000000002
>>
>>
>> ---
>> This bug is generated by a dumb bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for details.
>> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
>>
>> 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
>> If you want to test a patch for this bug, please reply with:
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>> #syz invalid
>> Note: if the crash happens again, it will cause creation of a new bug
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> I guess Paolo had already fixed it in this commit:
>
> commit 3f34cfae1238848fd53f25e5c8fd59da57901f4b
> Author: Paolo Abeni <pabeni@xxxxxxxxxx>
> Date:   Tue Jan 30 19:01:40 2018 +0100
>
>     netfilter: on sockopt() acquire sock lock only in the required scope
>
> Pls check if it's already in this kernel.


"netfilter: on sockopt() acquire sock lock only in the required scope"
wasn't yet in the upstream tree when the bug was detected.
Let's tell syzbot that this is fixed:

#syz fix: netfilter: on sockopt() acquire sock lock only in the required scope