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* [syzbot] [rdma?] possible deadlock in rds_trans_get_preferred
@ 2026-10-18 19:14 syzbot
  2026-10-19  1:51 ` Hillf Danton
  2026-10-19  8:04 ` Hillf Danton
  0 siblings, 2 replies; 5+ messages in thread
From: syzbot @ 2026-10-18 19:14 UTC (permalink / raw)
  To: linux-kernel, linux-rdma, syzkaller-bugs

Hello,

syzbot found the following issue on:

HEAD commit:    70dd4ee72eb2 Merge tag 'pinctrl-v7.3-3' of git://git.kerne..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1271a69c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=44ac479246d4559b
dashboard link: https://syzkaller.appspot.com/bug?extid=ccdb5058c3df2d94811c
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15b9618e580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ccdb5058c3df2d94811c@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/2:3/5905 is trying to acquire lock:
ffffffff9205e888 (rds_trans_sem){++++}-{4:4}, at: rds_trans_get_preferred+0xf7/0x2c0 net/rds/transport.c:100

but task is already holding lock:
ffff888014aed420 (&id_priv->handler_mutex/1){+.+.}-{4:4}, at: cma_ib_req_handler+0x16ff/0x5700 drivers/infiniband/core/cma.c:2450

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&id_priv->handler_mutex/1){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       cma_ib_req_handler+0x16ff/0x5700 drivers/infiniband/core/cma.c:2450
       cm_process_work+0x46/0x440 drivers/infiniband/core/cm.c:1869
       cm_queue_work_unlock+0x5d/0x250 drivers/infiniband/core/cm.c:933
       cm_req_handler drivers/infiniband/core/cm.c:2235 [inline]
       cm_work_handler+0x638d/0xc860 drivers/infiniband/core/cm.c:3849
       process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
       process_scheduled_works kernel/workqueue.c:3479 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&id_priv->handler_mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       rdma_destroy_id+0x1b/0x30 drivers/infiniband/core/cma.c:2124
       rds_ib_laddr_check_cm net/rds/ib.c:489 [inline]
       rds_ib_laddr_check+0x38b/0x730 net/rds/ib.c:511
       rds_trans_get_preferred+0x15f/0x2c0 net/rds/transport.c:104
       rds_bind+0x1a4a/0x2420 net/rds/bind.c:254
       __sys_bind_socket net/socket.c:1945 [inline]
       __sys_bind_socket net/socket.c:1937 [inline]
       __sys_bind+0x1a9/0x260 net/socket.c:1976
       __do_compat_sys_socketcall net/compat.c:450 [inline]
       __se_compat_sys_socketcall net/compat.c:422 [inline]
       __ia32_compat_sys_socketcall+0x4c7/0x770 net/compat.c:422
       do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
       __do_fast_syscall_32+0x13a/0x8b0 arch/x86/entry/syscall_32.c:291
       do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:316
       entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #0 (rds_trans_sem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       rds_trans_get_preferred+0xf7/0x2c0 net/rds/transport.c:100
       __rds_conn_create+0xad5/0x2650 net/rds/connection.c:252
       rds_conn_create+0x44/0x60 net/rds/connection.c:384
       rds_ib_cm_handle_connect+0x62b/0x1220 net/rds/ib_cm.c:860
       rds_rdma_cm_event_handler_cmn+0x59f/0x9b0 net/rds/rdma_transport.c:91
       cma_listen_handler+0x11a/0x180 drivers/infiniband/core/cma.c:2716
       cma_cm_event_handler+0x99/0x300 drivers/infiniband/core/cma.c:2181
       cma_ib_req_handler+0x1be2/0x5700 drivers/infiniband/core/cma.c:2461
       cm_process_work+0x46/0x440 drivers/infiniband/core/cm.c:1869
       cm_queue_work_unlock+0x5d/0x250 drivers/infiniband/core/cm.c:933
       cm_req_handler drivers/infiniband/core/cm.c:2235 [inline]
       cm_work_handler+0x638d/0xc860 drivers/infiniband/core/cm.c:3849
       process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
       process_scheduled_works kernel/workqueue.c:3479 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  rds_trans_sem --> &id_priv->handler_mutex --> &id_priv->handler_mutex/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&id_priv->handler_mutex/1);
                               lock(&id_priv->handler_mutex);
                               lock(&id_priv->handler_mutex/1);
  rlock(rds_trans_sem);

 *** DEADLOCK ***

locks held by kworker/2:3/5905: 4, last CPU#2:
 #0: ffff88804c131140 ((wq_completion)ib_cm){+.+.}-{0:0}, at: process_one_work+0x1466/0x1b10 kernel/workqueue.c:3371
 #1: ffffc900030dfd08 ((work_completion)(&(&work->work)->work)){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3372
 #2: ffff88802a6fc420 (&id_priv->handler_mutex){+.+.}-{4:4}, at: cma_ib_req_handler+0xef1/0x5700 drivers/infiniband/core/cma.c:2427
 #3: ffff888014aed420 (&id_priv->handler_mutex/1){+.+.}-{4:4}, at: cma_ib_req_handler+0x16ff/0x5700 drivers/infiniband/core/cma.c:2450

stack backtrace:
CPU: 2 UID: 0 PID: 5905 Comm: kworker/2:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: ib_cm cm_work_handler
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
 lock_acquire kernel/locking/lockdep.c:5942 [inline]
 lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 rds_trans_get_preferred+0xf7/0x2c0 net/rds/transport.c:100
 __rds_conn_create+0xad5/0x2650 net/rds/connection.c:252
 rds_conn_create+0x44/0x60 net/rds/connection.c:384
 rds_ib_cm_handle_connect+0x62b/0x1220 net/rds/ib_cm.c:860
 rds_rdma_cm_event_handler_cmn+0x59f/0x9b0 net/rds/rdma_transport.c:91
 cma_listen_handler+0x11a/0x180 drivers/infiniband/core/cma.c:2716
 cma_cm_event_handler+0x99/0x300 drivers/infiniband/core/cma.c:2181
 cma_ib_req_handler+0x1be2/0x5700 drivers/infiniband/core/cma.c:2461
 cm_process_work+0x46/0x440 drivers/infiniband/core/cm.c:1869
 cm_queue_work_unlock+0x5d/0x250 drivers/infiniband/core/cm.c:933
 cm_req_handler drivers/infiniband/core/cm.c:2235 [inline]
 cm_work_handler+0x638d/0xc860 drivers/infiniband/core/cm.c:3849
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
RDS/IB: Active conn connected <::ffff:172.20.20.170,::ffff:172.20.20.170,0> version 3.1


---
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^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2026-10-19  8:24 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2026-10-18 19:14 [syzbot] [rdma?] possible deadlock in rds_trans_get_preferred syzbot
2026-10-19  1:51 ` Hillf Danton
2026-10-19  1:51   ` syzbot
2026-10-19  8:04 ` Hillf Danton
2026-10-19  8:24   ` syzbot

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