Date:   Thu, 19 Aug 2021 12:16:19 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     zhoufeng <zhoufeng.zf@...edance.com>
Cc:     anthony.l.nguyen@...el.com, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, hawk@...nel.org,
        john.fastabend@...il.com, jeffrey.t.kirsher@...el.com,
        magnus.karlsson@...el.com, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, duanxiongchun@...edance.com,
        songmuchun@...edance.com, zhouchengming@...edance.com,
        chenying.kernel@...edance.com, zhengqi.arch@...edance.com,
        wangdongdong.6@...edance.com
Subject: Re: [External] Re: [PATCH] ixgbe: Fix NULL pointer dereference in
 ixgbe_xdp_setup

On Wed, Aug 18, 2021 at 04:30:15PM +0800, zhoufeng wrote:
> 
> 
> 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@...edance.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?

Yes, in general you can refer to
drivers/net/ethernet/intel/ice/ice_ethtool.c and in particular:

/**
 * ice_get_max_rxq - return the maximum number of Rx queues for in a PF
 * @pf: PF structure
 */
static int ice_get_max_rxq(struct ice_pf *pf)
{
	return min3(pf->num_lan_msix, (u16)num_online_cpus(),
		    (u16)pf->hw.func_caps.common_cap.num_rxq);
}


> 
> > 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@...edance.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
> > > 

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