Re: possible deadlock in rhashtable_lookup_insert_fast

[Cong Wang]

On Mon, Aug 13, 2018 at 11:21 PM syzbot
<syzbot+b66a5a554991a8ed027c@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    36d2f761b5aa cxgb4: update 1.20.8.0 as the latest firmware..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=134b323c400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=dbf55ebfa6bfd517
> dashboard link: https://syzkaller.appspot.com/bug?extid=b66a5a554991a8ed027c
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=103285f0400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12859d72400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+b66a5a554991a8ed027c@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> netlink: 'syz-executor077': attribute type 8 has an invalid length.
>
> ============================================
> WARNING: possible recursive locking detected
> 4.18.0-rc8+ #179 Not tainted
> --------------------------------------------
> syz-executor077/4391 is trying to acquire lock:
> (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at: spin_lock_bh
> include/linux/spinlock.h:315 [inline]
> (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at: __rhashtable_insert_fast
> include/linux/rhashtable.h:596 [inline]
> (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at:
> rhashtable_lookup_insert_fast.constprop.26+0x436/0x13a0
> include/linux/rhashtable.h:784
>
> but task is already holding lock:
> (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at: spin_lock
> include/linux/spinlock.h:310 [inline]
> (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at: ila_add_mapping
> net/ipv6/ila/ila_xlat.c:233 [inline]
> (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at:
> ila_xlat_nl_cmd_add_mapping+0x6bb/0x17e0 net/ipv6/ila/ila_xlat.c:355
>
> other info that might help us debug this:
>   Possible unsafe locking scenario:
>
>         CPU0
>         ----
>    lock(&(&tlocks[i])->rlock);
>    lock(&(&tlocks[i])->rlock);
>
>   *** DEADLOCK ***
>
>   May be due to missing lock nesting notation
>
> 3 locks held by syz-executor077/4391:
>   #0: (____ptrval____) (cb_lock){++++}, at: genl_rcv+0x19/0x40
> net/netlink/genetlink.c:636
>   #1: (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at: spin_lock
> include/linux/spinlock.h:310 [inline]
>   #1: (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at: ila_add_mapping
> net/ipv6/ila/ila_xlat.c:233 [inline]
>   #1: (____ptrval____) (&(&tlocks[i])->rlock){+.+.}, at:
> ila_xlat_nl_cmd_add_mapping+0x6bb/0x17e0 net/ipv6/ila/ila_xlat.c:355
>   #2: (____ptrval____) (rcu_read_lock){....}, at: __rhashtable_insert_fast
> include/linux/rhashtable.h:579 [inline]
>   #2: (____ptrval____) (rcu_read_lock){....}, at:
> rhashtable_lookup_insert_fast.constprop.26+0x1d7/0x13a0
> include/linux/rhashtable.h:784
>
> stack backtrace:
> CPU: 1 PID: 4391 Comm: syz-executor077 Not tainted 4.18.0-rc8+ #179
> 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+0x1c9/0x2b4 lib/dump_stack.c:113
>   print_deadlock_bug kernel/locking/lockdep.c:1765 [inline]
>   check_deadlock kernel/locking/lockdep.c:1809 [inline]
>   validate_chain kernel/locking/lockdep.c:2405 [inline]
>   __lock_acquire.cold.65+0x1fb/0x486 kernel/locking/lockdep.c:3435
>   lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924
>   __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
>   _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168
>   spin_lock_bh include/linux/spinlock.h:315 [inline]
>   __rhashtable_insert_fast include/linux/rhashtable.h:596 [inline]
>   rhashtable_lookup_insert_fast.constprop.26+0x436/0x13a0
> include/linux/rhashtable.h:784
>   ila_add_mapping net/ipv6/ila/ila_xlat.c:240 [inline]
>   ila_xlat_nl_cmd_add_mapping+0xafe/0x17e0 net/ipv6/ila/ila_xlat.c:355


Purely bogus warning introduced by commit
b893281715ab ("ila: Call library function alloc_bucket_locks").



>   genl_family_rcv_msg+0x8a3/0x1140 net/netlink/genetlink.c:601
>   genl_rcv_msg+0xc6/0x168 net/netlink/genetlink.c:626
>   netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2454
>   genl_rcv+0x28/0x40 net/netlink/genetlink.c:637
>   netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
>   netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1343
>   netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1908
>   sock_sendmsg_nosec net/socket.c:640 [inline]
>   sock_sendmsg+0xd5/0x120 net/socket.c:650
>   ___sys_sendmsg+0x7fd/0x930 net/socket.c:2133
>   __sys_sendmsg+0x11d/0x290 net/socket.c:2171
>   __do_sys_sendmsg net/socket.c:2180 [inline]
>   __se_sys_sendmsg net/socket.c:2178 [inline]
>   __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2178
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4400e9
> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffd14495758 EFLAG
>
>
> ---
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