Re: [External] Re: [PATCH] ixgbe: Fix NULL pointer dereference in ixgbe_xdp_setup

[zhoufeng <zhoufeng.zf@bytedance.com>]

在 2021/8/17 下午7:10, Maciej Fijalkowski 写道:
> On Tue, Aug 17, 2021 at 03:54:07PM +0800, Feng zhou wrote:
>> From: Feng Zhou <zhoufeng.zf@bytedance.com>
>>
>> The ixgbe driver currently generates a NULL pointer dereference with
>> some machine (online cpus < 63). This is due to the fact that the
>> maximum value of num_xdp_queues is nr_cpu_ids. Code is in
>> "ixgbe_set_rss_queues"".
> 
> That's a good catch, but we should fix set channels callback so that it
> will not allow a setting of queues to be higher than the
> num_online_cpus().
> 
> Please also include the tree in the patch subject that you're directing
> the patch to.
> 

Ok, Besides it, I will add more code in "ixgbe_set_channels":
/* verify the number of channels does not exceed num_online_cpus */
if (count > num_online_cpus())
	return -EINVAL;
If user want set queues num to be higher than the num_online_cpus(),
return error(-EINVAL).

What do you think?

> I'd be also thankful if you Cc me on Intel XDP related patches.
> Thanks!
> 

Ok, of course.


>>
>> Here's how the problem repeats itself:
>> Some machine (online cpus < 63), And user set num_queues to 63 through
>> ethtool. Code is in the "ixgbe_set_channels",
>> adapter->ring_feature[RING_F_FDIR].limit = count;
>> It becames 63.
>> When user use xdp, "ixgbe_set_rss_queues" will set queues num.
>> adapter->num_rx_queues = rss_i;
>> adapter->num_tx_queues = rss_i;
>> adapter->num_xdp_queues = ixgbe_xdp_queues(adapter);
>> And rss_i's value is from
>> f = &adapter->ring_feature[RING_F_FDIR];
>> rss_i = f->indices = f->limit;
>> So "num_rx_queues" > "num_xdp_queues", when run to "ixgbe_xdp_setup",
>> for (i = 0; i < adapter->num_rx_queues; i++)
>> 	if (adapter->xdp_ring[i]->xsk_umem)
>> lead to panic.
>> Call trace:
>> [exception RIP: ixgbe_xdp+368]
>> RIP: ffffffffc02a76a0  RSP: ffff9fe16202f8d0  RFLAGS: 00010297
>> RAX: 0000000000000000  RBX: 0000000000000020  RCX: 0000000000000000
>> RDX: 0000000000000000  RSI: 000000000000001c  RDI: ffffffffa94ead90
>> RBP: ffff92f8f24c0c18   R8: 0000000000000000   R9: 0000000000000000
>> R10: ffff9fe16202f830  R11: 0000000000000000  R12: ffff92f8f24c0000
>> R13: ffff9fe16202fc01  R14: 000000000000000a  R15: ffffffffc02a7530
>> ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>>   7 [ffff9fe16202f8f0] dev_xdp_install at ffffffffa89fbbcc
>>   8 [ffff9fe16202f920] dev_change_xdp_fd at ffffffffa8a08808
>>   9 [ffff9fe16202f960] do_setlink at ffffffffa8a20235
>> 10 [ffff9fe16202fa88] rtnl_setlink at ffffffffa8a20384
>> 11 [ffff9fe16202fc78] rtnetlink_rcv_msg at ffffffffa8a1a8dd
>> 12 [ffff9fe16202fcf0] netlink_rcv_skb at ffffffffa8a717eb
>> 13 [ffff9fe16202fd40] netlink_unicast at ffffffffa8a70f88
>> 14 [ffff9fe16202fd80] netlink_sendmsg at ffffffffa8a71319
>> 15 [ffff9fe16202fdf0] sock_sendmsg at ffffffffa89df290
>> 16 [ffff9fe16202fe08] __sys_sendto at ffffffffa89e19c8
>> 17 [ffff9fe16202ff30] __x64_sys_sendto at ffffffffa89e1a64
>> 18 [ffff9fe16202ff38] do_syscall_64 at ffffffffa84042b9
>> 19 [ffff9fe16202ff50] entry_SYSCALL_64_after_hwframe at ffffffffa8c0008c
>>
>> Fixes: 4a9b32f30f80 ("ixgbe: fix potential RX buffer starvation for
>> AF_XDP")
>> Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
>> ---
>>   drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
>> index 14aea40da50f..5db496cc5070 100644
>> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
>> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
>> @@ -10112,6 +10112,7 @@ static int ixgbe_xdp_setup(struct net_device *dev, struct bpf_prog *prog)
>>   	struct ixgbe_adapter *adapter = netdev_priv(dev);
>>   	struct bpf_prog *old_prog;
>>   	bool need_reset;
>> +	int num_queues;
>>   
>>   	if (adapter->flags & IXGBE_FLAG_SRIOV_ENABLED)
>>   		return -EINVAL;
>> @@ -10161,11 +10162,14 @@ static int ixgbe_xdp_setup(struct net_device *dev, struct bpf_prog *prog)
>>   	/* Kick start the NAPI context if there is an AF_XDP socket open
>>   	 * on that queue id. This so that receiving will start.
>>   	 */
>> -	if (need_reset && prog)
>> -		for (i = 0; i < adapter->num_rx_queues; i++)
>> +	if (need_reset && prog) {
>> +		num_queues = min_t(int, adapter->num_rx_queues,
>> +			adapter->num_xdp_queues);
>> +		for (i = 0; i < num_queues; i++)
>>   			if (adapter->xdp_ring[i]->xsk_pool)
>>   				(void)ixgbe_xsk_wakeup(adapter->netdev, i,
>>   						       XDP_WAKEUP_RX);
>> +	}
>>   
>>   	return 0;
>>   }
>> -- 
>> 2.11.0
>>