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net: Prevent infinite while loop in skb_tx_hash() 

commit 0c57eeecc559ca6bc18b8c4e2808bc78dbe769b0 upstream.

Drivers call netdev_set_num_tc() and then netdev_set_tc_queue()
to set the queue count and offset for each TC.  So the queue count
and offset for the TCs may be zero for a short period after dev->num_tc
has been set.  If a TX packet is being transmitted at this time in the
code path netdev_pick_tx() -> skb_tx_hash(), skb_tx_hash() may see
nonzero dev->num_tc but zero qcount for the TC.  The while loop that
keeps looping while hash >= qcount will not end.

Fix it by checking the TC's qcount to be nonzero before using it.

Fixes: eadec877ce ("net: Add support for subordinate traffic classes to netdev_pick_tx")
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Michael Chan 2021-10-25 05:05:28 -04:00 committed by Greg Kroah-Hartman
parent 6422e84718
commit 18a012869f
1 changed files with 6 additions and 0 deletions
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6
net/core/dev.c
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@ -2787,6 +2787,12 @@ static u16 skb_tx_hash(const struct net_device *dev,
qoffset = sb_dev->tc_to_txq[tc].offset;
qcount = sb_dev->tc_to_txq[tc].count;
if (unlikely(!qcount)) {
net_warn_ratelimited("%s: invalid qcount, qoffset %u for tc %u\n",
sb_dev->name, qoffset, tc);
qoffset = 0;
qcount = dev->real_num_tx_queues;
}
}
if (skb_rx_queue_recorded(skb)) {