Re: [syzbot] [net?] possible deadlock in inet6_getname

[Fernando Fernandez Mancera <fmancera@suse.de>]

On 2/13/26 1:15 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    57be33f85e36 nfc: nxp-nci: remove interrupt trigger type
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=12f2165a580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2c36acc86fd56a9d
> dashboard link: https://syzkaller.appspot.com/bug?extid=5efae91f60932839f0a5
> compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1584065a580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16f2165a580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/77aaa9b6c846/disk-57be33f8.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/2617a56e7118/vmlinux-57be33f8.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4fd173f33f5f/bzImage-57be33f8.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5efae91f60932839f0a5@syzkaller.appspotmail.com
> 
> ============================================
> 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
> 
> 
> ---
> This report 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 issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:
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> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
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> 
> If you want to undo deduplication, reply with:
> #syz undup
> 

#syz test

diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index 6fb5c928b8fd..a36e5dfd6c66 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -59,30 +59,12 @@ void rds_tcp_keepalive(struct socket *sock)
  static int
  rds_tcp_get_peer_sport(struct socket *sock)
  {
-	union {
-		struct sockaddr_storage storage;
-		struct sockaddr addr;
-		struct sockaddr_in sin;
-		struct sockaddr_in6 sin6;
-	} saddr;
-	int sport;
-
-	if (kernel_getpeername(sock, &saddr.addr) >= 0) {
-		switch (saddr.addr.sa_family) {
-		case AF_INET:
-			sport = ntohs(saddr.sin.sin_port);
-			break;
-		case AF_INET6:
-			sport = ntohs(saddr.sin6.sin6_port);
-			break;
-		default:
-			sport = -1;
-		}
-	} else {
-		sport = -1;
-	}
+	struct sock *sk = sock->sk;
+
+	if (!sk)
+		return -1;

-	return sport;
+	return ntohs(inet_sk(sk)->inet_dport);
  }

  /* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the