Kernel bug: possible deadlock in inet6_getname
Subsystem: net
Status: fixed

Crash report:
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u8:6/2985 is trying to acquire lock:
ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: inet6_getname+0x15d/0x650 net/ipv6/af_inet6.c:533

but task is already holding lock:
ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: tcp_sock_set_cork+0x2c/0x2e0 net/ipv4/tcp.c:3694

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(k-sk_lock-AF_INET6);
  lock(k-sk_lock-AF_INET6);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by kworker/u8:6/2985:
 #0: ffff888033131948 ((wq_completion)krds_cp_wq#1/0){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline]
 #0: ffff888033131948 ((wq_completion)krds_cp_wq#1/0){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0 kernel/workqueue.c:3340
 #1: ffffc9000b8a7bc0 ((work_completion)(&(&cp->cp_send_w)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline]
 #1: ffffc9000b8a7bc0 ((work_completion)(&(&cp->cp_send_w)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0 kernel/workqueue.c:3340
 #2: ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline]
 #2: ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: tcp_sock_set_cork+0x2c/0x2e0 net/ipv4/tcp.c:3694
 #3: ffff88807a07abc8 (k-clock-AF_INET6){++.-}-{3:3}, at: rds_tcp_data_ready+0x113/0x950 net/rds/tcp_recv.c:320

stack backtrace:
CPU: 1 UID: 0 PID: 2985 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Workqueue: krds_cp_wq#1/0 rds_send_worker
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x253f/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868
 lock_sock_nested+0x48/0x100 net/core/sock.c:3780
 lock_sock include/net/sock.h:1709 [inline]
 inet6_getname+0x15d/0x650 net/ipv6/af_inet6.c:533
 rds_tcp_get_peer_sport net/rds/tcp_listen.c:70 [inline]
 rds_tcp_conn_slots_available+0x288/0x470 net/rds/tcp_listen.c:149
 rds_recv_hs_exthdrs+0x60f/0x7c0 net/rds/recv.c:265
 rds_recv_incoming+0x9f6/0x12d0 net/rds/recv.c:389
 rds_tcp_data_recv+0x7f1/0xa40 net/rds/tcp_recv.c:243
 __tcp_read_sock+0x196/0x970 net/ipv4/tcp.c:1702
 rds_tcp_read_sock net/rds/tcp_recv.c:277 [inline]
 rds_tcp_data_ready+0x369/0x950 net/rds/tcp_recv.c:331
 tcp_rcv_established+0x19e9/0x2670 net/ipv4/tcp_input.c:6675
 tcp_v6_do_rcv+0x8eb/0x1ba0 net/ipv6/tcp_ipv6.c:1609
 sk_backlog_rcv include/net/sock.h:1185 [inline]
 __release_sock+0x1b8/0x3a0 net/core/sock.c:3213
 release_sock+0x5f/0x1f0 net/core/sock.c:3795
 rds_send_xmit+0x207e/0x28d0 net/rds/send.c:480
 rds_send_worker+0x7d/0x2e0 net/rds/threads.c:200
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xaec/0x17a0 kernel/workqueue.c:3340
 worker_thread+0xda6/0x1360 kernel/workqueue.c:3421
 kthread+0x726/0x8b0 kernel/kthread.c:463
 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
BUG: sleeping function called from invalid context at net/core/sock.c:3782
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2985, name: kworker/u8:6
preempt_count: 201, expected: 0
RCU nest depth: 0, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 2985 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Workqueue: krds_cp_wq#1/0 rds_send_worker
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 __might_resched+0x378/0x4d0 kernel/sched/core.c:8829
 lock_sock_nested+0x5d/0x100 net/core/sock.c:3782
 lock_sock include/net/sock.h:1709 [inline]
 inet6_getname+0x15d/0x650 net/ipv6/af_inet6.c:533
 rds_tcp_get_peer_sport net/rds/tcp_listen.c:70 [inline]
 rds_tcp_conn_slots_available+0x288/0x470 net/rds/tcp_listen.c:149
 rds_recv_hs_exthdrs+0x60f/0x7c0 net/rds/recv.c:265
 rds_recv_incoming+0x9f6/0x12d0 net/rds/recv.c:389
 rds_tcp_data_recv+0x7f1/0xa40 net/rds/tcp_recv.c:243
 __tcp_read_sock+0x196/0x970 net/ipv4/tcp.c:1702
 rds_tcp_read_sock net/rds/tcp_recv.c:277 [inline]
 rds_tcp_data_ready+0x369/0x950 net/rds/tcp_recv.c:331
 tcp_rcv_established+0x19e9/0x2670 net/ipv4/tcp_input.c:6675
 tcp_v6_do_rcv+0x8eb/0x1ba0 net/ipv6/tcp_ipv6.c:1609
 sk_backlog_rcv include/net/sock.h:1185 [inline]
 __release_sock+0x1b8/0x3a0 net/core/sock.c:3213
 release_sock+0x5f/0x1f0 net/core/sock.c:3795
 rds_send_xmit+0x207e/0x28d0 net/rds/send.c:480
 rds_send_worker+0x7d/0x2e0 net/rds/threads.c:200
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xaec/0x17a0 kernel/workqueue.c:3340
 worker_thread+0xda6/0x1360 kernel/workqueue.c:3421
 kthread+0x726/0x8b0 kernel/kthread.c:463
 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
BUG: scheduling while atomic: kworker/u8:6/2985/0x00000202
INFO: lockdep is turned off.
Modules linked in:
Preemption disabled at:
[<0000000000000000>] 0x0