linux-hardening - [PATCH v2] net/net_failover: fix txq exceeding warning

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Date:   Fri, 24 Mar 2023 17:19:54 +0800
From:   Faicker Mo <faicker.mo@...oud.cn>
To:     faicker.mo@...oud.cn
Cc:     Sridhar Samudrala <sridhar.samudrala@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Kees Cook <keescook@...omium.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v2] net/net_failover: fix txq exceeding warning

The failover txq is inited as 16 queues.
when a packet is transmitted from the failover device firstly,
the failover device will select the queue which is returned from
the primary device if the primary device is UP and running.
If the primary device txq is bigger than the default 16,
it can lead to the following warning:
eth0 selects TX queue 18, but real number of TX queues is 16

The warning backtrace is:
[   32.146376] CPU: 18 PID: 9134 Comm: chronyd Tainted: G            E      6.2.8-1.el7.centos.x86_64 #1
[   32.147175] Hardware name: Red Hat KVM, BIOS 1.10.2-3.el7_4.1 04/01/2014
[   32.147730] Call Trace:
[   32.147971]  <TASK>
[   32.148183]  dump_stack_lvl+0x48/0x70
[   32.148514]  dump_stack+0x10/0x20
[   32.148820]  netdev_core_pick_tx+0xb1/0xe0
[   32.149180]  __dev_queue_xmit+0x529/0xcf0
[   32.149533]  ? __check_object_size.part.0+0x21c/0x2c0
[   32.149967]  ip_finish_output2+0x278/0x560
[   32.150327]  __ip_finish_output+0x1fe/0x2f0
[   32.150690]  ip_finish_output+0x2a/0xd0
[   32.151032]  ip_output+0x7a/0x110
[   32.151337]  ? __pfx_ip_finish_output+0x10/0x10
[   32.151733]  ip_local_out+0x5e/0x70
[   32.152054]  ip_send_skb+0x19/0x50
[   32.152366]  udp_send_skb.isra.0+0x163/0x3a0
[   32.152736]  udp_sendmsg+0xba8/0xec0
[   32.153060]  ? __folio_memcg_unlock+0x25/0x60
[   32.153445]  ? __pfx_ip_generic_getfrag+0x10/0x10
[   32.153854]  ? sock_has_perm+0x85/0xa0
[   32.154190]  inet_sendmsg+0x6d/0x80
[   32.154508]  ? inet_sendmsg+0x6d/0x80
[   32.154838]  sock_sendmsg+0x62/0x70
[   32.155152]  ____sys_sendmsg+0x134/0x290
[   32.155499]  ___sys_sendmsg+0x81/0xc0
[   32.155828]  ? _get_random_bytes.part.0+0x79/0x1a0
[   32.156240]  ? ip4_datagram_release_cb+0x5f/0x1e0
[   32.156649]  ? get_random_u16+0x69/0xf0
[   32.156989]  ? __fget_light+0xcf/0x110
[   32.157326]  __sys_sendmmsg+0xc4/0x210
[   32.157657]  ? __sys_connect+0xb7/0xe0
[   32.157995]  ? __audit_syscall_entry+0xce/0x140
[   32.158388]  ? syscall_trace_enter.isra.0+0x12c/0x1a0
[   32.158820]  __x64_sys_sendmmsg+0x24/0x30
[   32.159171]  do_syscall_64+0x38/0x90
[   32.159493]  entry_SYSCALL_64_after_hwframe+0x72/0xdc

Fix that by reducing txq number as the non-existent primary-dev does.

Fixes: cfc80d9a1163 ("net: Introduce net_failover driver")
Signed-off-by: Faicker Mo <faicker.mo@...oud.cn>
---
 drivers/net/net_failover.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/net/net_failover.c b/drivers/net/net_failover.c
index 7a28e082436e..d0c916a53d7c 100644
--- a/drivers/net/net_failover.c
+++ b/drivers/net/net_failover.c
@@ -130,14 +130,10 @@ static u16 net_failover_select_queue(struct net_device *dev,
 			txq = ops->ndo_select_queue(primary_dev, skb, sb_dev);
 		else
 			txq = netdev_pick_tx(primary_dev, skb, NULL);
-
-		qdisc_skb_cb(skb)->slave_dev_queue_mapping = skb->queue_mapping;
-
-		return txq;
+	} else {
+		txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : 0;
 	}
 
-	txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : 0;
-
 	/* Save the original txq to restore before passing to the driver */
 	qdisc_skb_cb(skb)->slave_dev_queue_mapping = skb->queue_mapping;
 
-- 
2.39.1