netdev - Re: [PATCH net] ionic: fix use after netif_napi

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Date: Tue, 11 Jun 2024 13:05:29 +0900
From: Taehee Yoo <ap420073@...il.com>
To: "Nelson, Shannon" <shannon.nelson@....com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	edumazet@...gle.com, brett.creeley@....com, drivers@...sando.io, 
	netdev@...r.kernel.org, jacob.e.keller@...el.com
Subject: Re: [PATCH net] ionic: fix use after netif_napi_del()

On Tue, Jun 11, 2024 at 3:21 AM Nelson, Shannon <shannon.nelson@....com> wrote:
>

Hi Nelson,
Thanks a lot for the review!

> On 6/9/2024 9:07 PM, Taehee Yoo wrote:
> >
> > 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@...il.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
> >
>
> I think a better solution would be to stay out of the napi internals
> altogether and rely on the IONIC_QCQ_F_INTR flag as in
> ionic_qcq_disable() and ionic_lif_qcq_deinit().
>
> Thanks for catching this. If I remember correctly, this is a vestige of
> an experimental feature that never went upstream, and eventually was
> dropped altogether anyway.
>
> sln

Okay, I will try to use ionic internal flags like IONIC_QCQ_F_INTR.
And then I will send a v2 patch after some tests.

Thanks a lot!
Taehee Yoo