Re: [syzbot] possible deadlock in smc_switch_to_fallback

[Jakub Kicinski]

Adding Alibaba folks to CC.

On Fri, 19 Nov 2021 18:47:22 -0800 syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    9539ba4308ad Merge tag 'riscv-for-linus-5.16-rc2' of git:/..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17f79d01b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6d3b8fd1977c1e73
> dashboard link: https://syzkaller.appspot.com/bug?extid=e979d3597f48262cb4ee
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e979d3597f48262cb4ee@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ============================================
> WARNING: possible recursive locking detected
> 5.16.0-rc1-syzkaller #0 Not tainted
> --------------------------------------------
> syz-executor.3/1337 is trying to acquire lock:
> ffff88809466ce58 (&ei->socket.wq.wait){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline]
> ffff88809466ce58 (&ei->socket.wq.wait){..-.}-{2:2}, at: smc_switch_to_fallback+0x3d5/0x8c0 net/smc/af_smc.c:588
> 
> but task is already holding lock:
> ffff88809466c258 (&ei->socket.wq.wait){..-.}-{2:2}, at: smc_switch_to_fallback+0x3ca/0x8c0 net/smc/af_smc.c:587
> 
> other info that might help us debug this:
>  Possible unsafe locking scenario:
> 
>        CPU0
>        ----
>   lock(&ei->socket.wq.wait);
>   lock(&ei->socket.wq.wait);
> 
>  *** DEADLOCK ***
> 
>  May be due to missing lock nesting notation
> 
> 2 locks held by syz-executor.3/1337:
>  #0: 
> ffff888082ba8120 (sk_lock-AF_SMC){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1645 [inline]
> ffff888082ba8120 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_setsockopt+0x2b7/0xa40 net/smc/af_smc.c:2449
>  #1: ffff88809466c258 (&ei->socket.wq.wait){..-.}-{2:2}, at: smc_switch_to_fallback+0x3ca/0x8c0 net/smc/af_smc.c:587
> 
> stack backtrace:
> CPU: 1 PID: 1337 Comm: syz-executor.3 Not tainted 5.16.0-rc1-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
>  check_deadlock kernel/locking/lockdep.c:2999 [inline]
>  validate_chain kernel/locking/lockdep.c:3788 [inline]
>  __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027
>  lock_acquire kernel/locking/lockdep.c:5637 [inline]
>  lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
>  __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
>  _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
>  spin_lock include/linux/spinlock.h:349 [inline]
>  smc_switch_to_fallback+0x3d5/0x8c0 net/smc/af_smc.c:588
>  smc_setsockopt+0x8ee/0xa40 net/smc/af_smc.c:2459
>  __sys_setsockopt+0x2db/0x610 net/socket.c:2176
>  __do_sys_setsockopt net/socket.c:2187 [inline]
>  __se_sys_setsockopt net/socket.c:2184 [inline]
>  __x64_sys_setsockopt+0xba/0x150 net/socket.c:2184
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7fa2a8fceae9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fa2a6544188 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 00007fa2a90e1f60 RCX: 00007fa2a8fceae9
> RDX: 0000000000000021 RSI: 0000000000000006 RDI: 0000000000000005
> RBP: 00007fa2a9028f6d R08: 0000000000000010 R09: 0000000000000000
> R10: 0000000020000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffc2297067f R14: 00007fa2a6544300 R15: 0000000000022000
>  </TASK>
> 
> 
> ---
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> 
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