From: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
[ Upstream commit 7a61432dc81375be06b02f0061247d3efbdfce3a ]
Possible recursive locking is detected by lockdep when SMC
falls back to TCP. The corresponding warnings are as follows:
============================================
WARNING: possible recursive locking detected
5.16.0-rc1+ #18 Tainted: G E
--------------------------------------------
wrk/1391 is trying to acquire lock:
ffff975246c8e7d8 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0x109/0x250 [smc]
but task is already holding lock:
ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc]
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 wrk/1391:
#0: ffff975246040130 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_connect+0x43/0x150 [smc]
#1: ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc]
stack backtrace:
Call Trace:
<TASK>
dump_stack_lvl+0x56/0x7b
__lock_acquire+0x951/0x11f0
lock_acquire+0x27a/0x320
? smc_switch_to_fallback+0x109/0x250 [smc]
? smc_switch_to_fallback+0xfe/0x250 [smc]
_raw_spin_lock_irq+0x3b/0x80
? smc_switch_to_fallback+0x109/0x250 [smc]
smc_switch_to_fallback+0x109/0x250 [smc]
smc_connect_fallback+0xe/0x30 [smc]
__smc_connect+0xcf/0x1090 [smc]
? mark_held_locks+0x61/0x80
? __local_bh_enable_ip+0x77/0xe0
? lockdep_hardirqs_on+0xbf/0x130
? smc_connect+0x12a/0x150 [smc]
smc_connect+0x12a/0x150 [smc]
__sys_connect+0x8a/0xc0
? syscall_enter_from_user_mode+0x20/0x70
__x64_sys_connect+0x16/0x20
do_syscall_64+0x34/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
The nested locking in smc_switch_to_fallback() is considered to
possibly cause a deadlock because smc_wait->lock and clc_wait->lock
are the same type of lock. But actually it is safe so far since
there is no other place trying to obtain smc_wait->lock when
clc_wait->lock is held. So the patch replaces spin_lock() with
spin_lock_nested() to avoid false report by lockdep.
Link: https://lkml.org/lkml/2021/11/19/962
Fixes: 2153bd1e3d3d ("Transfer remaining wait queue entries during fallback")
Reported-by: syzbot+e979d3597f48262cb4ee@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
Acked-by: Tony Lu <tonylu@xxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/smc/af_smc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index c0456cb7623cb..06e4a07bdcdc1 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -566,7 +566,7 @@ static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
* to clcsocket->wq during the fallback.
*/
spin_lock_irqsave(&smc_wait->lock, flags);
- spin_lock(&clc_wait->lock);
+ spin_lock_nested(&clc_wait->lock, SINGLE_DEPTH_NESTING);
list_splice_init(&smc_wait->head, &clc_wait->head);
spin_unlock(&clc_wait->lock);
spin_unlock_irqrestore(&smc_wait->lock, flags);
--
2.33.0
