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Date:   Tue, 17 Aug 2021 13:10:47 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@intel.com>
To:     Feng zhou <zhoufeng.zf@bytedance.com>
Cc:     jesse.brandeburg@intel.com, anthony.l.nguyen@intel.com,
        davem@davemloft.net, kuba@kernel.org, ast@kernel.org,
        daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com,
        jeffrey.t.kirsher@intel.com, magnus.karlsson@intel.com,
        intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
        duanxiongchun@bytedance.com, songmuchun@bytedance.com,
        zhouchengming@bytedance.com, chenying.kernel@bytedance.com,
        zhengqi.arch@bytedance.com, wangdongdong.6@bytedance.com
Subject: Re: [PATCH] ixgbe: Fix NULL pointer dereference in ixgbe_xdp_setup
Message-ID: <20210817111047.GA8143@ranger.igk.intel.com>
References: <20210817075407.11961-1-zhoufeng.zf@bytedance.com>
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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.

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

> 
> 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
>