[PATCH 6.4 161/800] wifi: ath9k: Fix possible stall on ath9k_txq_list_has_key()

Greg Kroah-Hartman
2023-07-16T20:00:19Z

From: Remi Pommarel <repk@triplefau.lt>

[ Upstream commit 75086cc6dee046e3fbb3dba148b376d8802f83bc ]

On EDMA capable hardware, ath9k_txq_list_has_key() can enter infinite
loop if it is called while all txq_fifos have packets that use different
key that the one we are looking for. Fix it by exiting the loop if all
txq_fifos have been checked already.

Because this loop is called under spin_lock_bh() (see ath_txq_lock) it
causes the following rcu stall:

rcu: INFO: rcu_sched self-detected stall on CPU
ath10k_pci 0000:01:00.0: failed to read temperature -11
rcu: 1-....: (5254 ticks this GP) idle=189/1/0x4000000000000002 softirq=8442983/8442984 fqs=2579
(t=5257 jiffies g=17983297 q=334)
Task dump for CPU 1:
task:hostapd state:R running task stack: 0 pid: 297 ppid: 289 flags:0x0000000a
Call trace:
dump_backtrace+0x0/0x170
show_stack+0x1c/0x24
sched_show_task+0x140/0x170
dump_cpu_task+0x48/0x54
rcu_dump_cpu_stacks+0xf0/0x134
rcu_sched_clock_irq+0x8d8/0x9fc
update_process_times+0xa0/0xec
tick_sched_timer+0x5c/0xd0
__hrtimer_run_queues+0x154/0x320
hrtimer_interrupt+0x120/0x2f0
arch_timer_handler_virt+0x38/0x44
handle_percpu_devid_irq+0x9c/0x1e0
handle_domain_irq+0x64/0x90
gic_handle_irq+0x78/0xb0
call_on_irq_stack+0x28/0x38
do_interrupt_handler+0x54/0x5c
el1_interrupt+0x2c/0x4c
el1h_64_irq_handler+0x14/0x1c
el1h_64_irq+0x74/0x78
ath9k_txq_has_key+0x1bc/0x250 [ath9k]
ath9k_set_key+0x1cc/0x3dc [ath9k]
drv_set_key+0x78/0x170
ieee80211_key_replace+0x564/0x6cc
ieee80211_key_link+0x174/0x220
ieee80211_add_key+0x11c/0x300
nl80211_new_key+0x12c/0x330
genl_family_rcv_msg_doit+0xbc/0x11c
genl_rcv_msg+0xd8/0x1c4
netlink_rcv_skb+0x40/0x100
genl_rcv+0x3c/0x50
netlink_unicast+0x1ec/0x2c0
netlink_sendmsg+0x198/0x3c0
____sys_sendmsg+0x210/0x250
___sys_sendmsg+0x78/0xc4
__sys_sendmsg+0x4c/0x90
__arm64_sys_sendmsg+0x28/0x30
invoke_syscall.constprop.0+0x60/0x100
do_el0_svc+0x48/0xd0
el0_svc+0x14/0x50
el0t_64_sync_handler+0xa8/0xb0
el0t_64_sync+0x158/0x15c

This rcu stall is hard to reproduce as is, but changing ATH_TXFIFO_DEPTH
from 8 to 2 makes it reasonably easy to reproduce.

Fixes: ca2848022c12 ("ath9k: Postpone key cache entry deletion for TXQ frames reference it")
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Tested-by: Nicolas Escande <nico.escande@gmail.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230609093744.1985-1-repk@triplefau.lt
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/ath/ath9k/main.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index a4197c14f0a92..7f9f06ea8a05f 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -850,7 +850,7 @@ static bool ath9k_txq_list_has_key(struct list_head *txq_list, u32 keyix)
static bool ath9k_txq_has_key(struct ath_softc *sc, u32 keyix)
{
struct ath_hw *ah = sc->sc_ah;
- int i;
+ int i, j;
struct ath_txq *txq;
bool key_in_use = false;

@@ -868,8 +868,9 @@ static bool ath9k_txq_has_key(struct ath_softc *sc, u32 keyix)
if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA) {
int idx = txq->txq_tailidx;

- while (!key_in_use &&
- !list_empty(&txq->txq_fifo[idx])) {
+ for (j = 0; !key_in_use &&
+ !list_empty(&txq->txq_fifo[idx]) &&
+ j < ATH_TXFIFO_DEPTH; j++) {
key_in_use = ath9k_txq_list_has_key(
&txq->txq_fifo[idx], keyix);
INCR(idx, ATH_TXFIFO_DEPTH);
--
2.39.2