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

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Message-ID: <d1b1d6fd-26be-46c5-b453-538ca5880e7b@amd.com>
Date: Mon, 10 Jun 2024 11:21:06 -0700
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Taehee Yoo <ap420073@...il.com>, davem@...emloft.net, kuba@...nel.org,
 pabeni@...hat.com, edumazet@...gle.com, brett.creeley@....com,
 drivers@...sando.io, netdev@...r.kernel.org
Cc: jacob.e.keller@...el.com, nitya.sunkad@....com
Subject: Re: [PATCH net] ionic: fix use after netif_napi_del()

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