netdev - Re: [PATCH net 1/1] ibmvnic: don't release napi in __ibmvnic

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Date:   Mon, 07 Feb 2022 18:59:50 -0800
From:   Dany Madden <drt@...ux.ibm.com>
To:     Sukadev Bhattiprolu <sukadev@...ux.ibm.com>
Cc:     netdev@...r.kernel.org, Brian King <brking@...ux.ibm.com>,
        Rick Lindsley <ricklind@...ux.ibm.com>, abdhalee@...ibm.com,
        vaish123@...ibm.com, Abdul Haleem <abdhalee@...ux.vnet.ibm.com>
Subject: Re: [PATCH net 1/1] ibmvnic: don't release napi in __ibmvnic_open()

On 2022-02-07 16:19, Sukadev Bhattiprolu wrote:
> If __ibmvnic_open() encounters an error such as when setting link 
> state,
> it calls release_resources() which frees the napi structures 
> needlessly.
> Instead, have __ibmvnic_open() only clean up the work it did so far 
> (i.e.
> disable napi and irqs) and leave the rest to the callers.
> 
> If caller of __ibmvnic_open() is ibmvnic_open(), it should release the
> resources immediately. If the caller is do_reset() or do_hard_reset(),
> they will release the resources on the next reset.
> 
> This fixes following crash that occured when running the drmgr command
> several times to add/remove a vnic interface:
> 
> 	[102056] ibmvnic 30000003 env3: Disabling rx_scrq[6] irq
> 	[102056] ibmvnic 30000003 env3: Disabling rx_scrq[7] irq
> 	[102056] ibmvnic 30000003 env3: Replenished 8 pools
> 	Kernel attempted to read user page (10) - exploit attempt? (uid: 0)
> 	BUG: Kernel NULL pointer dereference on read at 0x00000010
> 	Faulting instruction address: 0xc000000000a3c840
> 	Oops: Kernel access of bad area, sig: 11 [#1]
> 	LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
> 	...
> 	CPU: 9 PID: 102056 Comm: kworker/9:2 Kdump: loaded Not tainted
> 5.16.0-rc5-autotest-g6441998e2e37 #1
> 	Workqueue: events_long __ibmvnic_reset [ibmvnic]
> 	NIP:  c000000000a3c840 LR: c0080000029b5378 CTR: c000000000a3c820
> 	REGS: c0000000548e37e0 TRAP: 0300   Not tainted
> (5.16.0-rc5-autotest-g6441998e2e37)
> 	MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 28248484  XER: 
> 00000004
> 	CFAR: c0080000029bdd24 DAR: 0000000000000010 DSISR: 40000000 IRQMASK: 
> 0
> 	GPR00: c0080000029b55d0 c0000000548e3a80 c0000000028f0200 
> 0000000000000000
> 	...
> 	NIP [c000000000a3c840] napi_enable+0x20/0xc0
> 	LR [c0080000029b5378] __ibmvnic_open+0xf0/0x430 [ibmvnic]
> 	Call Trace:
> 	[c0000000548e3a80] [0000000000000006] 0x6 (unreliable)
> 	[c0000000548e3ab0] [c0080000029b55d0] __ibmvnic_open+0x348/0x430 
> [ibmvnic]
> 	[c0000000548e3b40] [c0080000029bcc28] __ibmvnic_reset+0x500/0xdf0 
> [ibmvnic]
> 	[c0000000548e3c60] [c000000000176228] process_one_work+0x288/0x570
> 	[c0000000548e3d00] [c000000000176588] worker_thread+0x78/0x660
> 	[c0000000548e3da0] [c0000000001822f0] kthread+0x1c0/0x1d0
> 	[c0000000548e3e10] [c00000000000cf64] ret_from_kernel_thread+0x5c/0x64
> 	Instruction dump:
> 	7d2948f8 792307e0 4e800020 60000000 3c4c01eb 384239e0 f821ffd1 
> 39430010
> 	38a0fff6 e92d1100 f9210028 39200000 <e9030010> f9010020 60420000 
> e9210020
> 	---[ end trace 5f8033b08fd27706 ]---
> 
> Fixes: ed651a10875f ("ibmvnic: Updated reset handling)
> Reported-by: Abdul Haleem <abdhalee@...ux.vnet.ibm.com>
> Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.ibm.com>
Reviewed-by: Dany Madden <drt@...ux.ibm.com>

> ---
>  drivers/net/ethernet/ibm/ibmvnic.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
> b/drivers/net/ethernet/ibm/ibmvnic.c
> index f5d1ba9bea48..50d2e48274eb 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -110,6 +110,7 @@ static void ibmvnic_tx_scrq_clean_buffer(struct
> ibmvnic_adapter *adapter,
>  					 struct ibmvnic_sub_crq_queue *tx_scrq);
>  static void free_long_term_buff(struct ibmvnic_adapter *adapter,
>  				struct ibmvnic_long_term_buff *ltb);
> +static void ibmvnic_disable_irqs(struct ibmvnic_adapter *adapter);
> 
>  struct ibmvnic_stat {
>  	char name[ETH_GSTRING_LEN];
> @@ -1424,7 +1425,7 @@ static int __ibmvnic_open(struct net_device 
> *netdev)
>  	rc = set_link_state(adapter, IBMVNIC_LOGICAL_LNK_UP);
>  	if (rc) {
>  		ibmvnic_napi_disable(adapter);
> -		release_resources(adapter);
> +		ibmvnic_disable_irqs(adapter);
>  		return rc;
>  	}
> 
> @@ -1474,9 +1475,6 @@ static int ibmvnic_open(struct net_device 
> *netdev)
>  		rc = init_resources(adapter);
>  		if (rc) {
>  			netdev_err(netdev, "failed to initialize resources\n");
> -			release_resources(adapter);
> -			release_rx_pools(adapter);
> -			release_tx_pools(adapter);
>  			goto out;
>  		}
>  	}
> @@ -1493,6 +1491,13 @@ static int ibmvnic_open(struct net_device 
> *netdev)
>  		adapter->state = VNIC_OPEN;
>  		rc = 0;
>  	}
> +
> +	if (rc) {
> +		release_resources(adapter);
> +		release_rx_pools(adapter);
> +		release_tx_pools(adapter);
> +	}
> +
>  	return rc;
>  }