[PATCH net] ionic: fix use after netif_napi_del()

[Taehee Yoo <ap420073@gmail.com>]

When queues are started, netif_napi_add() and napi_enable() are called.
If there are 4 queues and only 3 queues are used for the current
configuration, only 3 queues' napi should be registered and enabled.
The ionic_qcq_enable() checks whether the .poll pointer is not NULL for
enabling only the using queue' napi. Unused queues' napi will not be
registered by netif_napi_add(), so the .poll pointer indicates NULL.
But it couldn't distinguish whether the napi was unregistered or not
because netif_napi_del() doesn't reset the .poll pointer to NULL.
So, ionic_qcq_enable() calls napi_enable() for the queue, which was
unregistered by netif_napi_del().

Reproducer:
   ethtool -L <interface name> rx 1 tx 1 combined 0
   ethtool -L <interface name> rx 0 tx 0 combined 1
   ethtool -L <interface name> rx 0 tx 0 combined 4

Splat looks like:
kernel BUG at net/core/dev.c:6666!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 3 PID: 1057 Comm: kworker/3:3 Not tainted 6.10.0-rc2+ #16
Workqueue: events ionic_lif_deferred_work [ionic]
RIP: 0010:napi_enable+0x3b/0x40
Code: 48 89 c2 48 83 e2 f6 80 b9 61 09 00 00 00 74 0d 48 83 bf 60 01 00 00 00 74 03 80 ce 01 f0 4f
RSP: 0018:ffffb6ed83227d48 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff97560cda0828 RCX: 0000000000000029
RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff97560cda0a28
RBP: ffffb6ed83227d50 R08: 0000000000000400 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: ffff97560ce3c1a0 R14: 0000000000000000 R15: ffff975613ba0a20
FS:  0000000000000000(0000) GS:ffff975d5f780000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f734ee200 CR3: 0000000103e50000 CR4: 00000000007506f0
PKRU: 55555554
Call Trace:
 <TASK>
 ? die+0x33/0x90
 ? do_trap+0xd9/0x100
 ? napi_enable+0x3b/0x40
 ? do_error_trap+0x83/0xb0
 ? napi_enable+0x3b/0x40
 ? napi_enable+0x3b/0x40
 ? exc_invalid_op+0x4e/0x70
 ? napi_enable+0x3b/0x40
 ? asm_exc_invalid_op+0x16/0x20
 ? napi_enable+0x3b/0x40
 ionic_qcq_enable+0xb7/0x180 [ionic 59bdfc8a035436e1c4224ff7d10789e3f14643f8]
 ionic_start_queues+0xc4/0x290 [ionic 59bdfc8a035436e1c4224ff7d10789e3f14643f8]
 ionic_link_status_check+0x11c/0x170 [ionic 59bdfc8a035436e1c4224ff7d10789e3f14643f8]
 ionic_lif_deferred_work+0x129/0x280 [ionic 59bdfc8a035436e1c4224ff7d10789e3f14643f8]
 process_one_work+0x145/0x360
 worker_thread+0x2bb/0x3d0
 ? __pfx_worker_thread+0x10/0x10
 kthread+0xcc/0x100
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x2d/0x50
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1a/0x30

Fixes: 0f3154e6bcb3 ("ionic: Add Tx and Rx handling")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---
 drivers/net/ethernet/pensando/ionic/ionic_lif.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_lif.c b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
index 24870da3f484..b66c907d88e6 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_lif.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
@@ -304,7 +304,7 @@ static int ionic_qcq_enable(struct ionic_qcq *qcq)
 	if (ret)
 		return ret;
 
-	if (qcq->napi.poll)
+	if (test_bit(NAPI_STATE_LISTED, &qcq->napi.state))
 		napi_enable(&qcq->napi);
 
 	if (qcq->flags & IONIC_QCQ_F_INTR) {
-- 
2.34.1