This is a note to let you know that I've just added the patch titled
net: Prevent infinite while loop in skb_tx_hash()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-prevent-infinite-while-loop-in-skb_tx_hash.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0c57eeecc559ca6bc18b8c4e2808bc78dbe769b0 Mon Sep 17 00:00:00 2001
From: Michael Chan <michael.chan@xxxxxxxxxxxx>
Date: Mon, 25 Oct 2021 05:05:28 -0400
Subject: net: Prevent infinite while loop in skb_tx_hash()
From: Michael Chan <michael.chan@xxxxxxxxxxxx>
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: eadec877ce9c ("net: Add support for subordinate traffic classes to netdev_pick_tx")
Reviewed-by: Andy Gospodarek <gospo@xxxxxxxxxxxx>
Signed-off-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/dev.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2846,6 +2846,12 @@ static u16 skb_tx_hash(const struct net_
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)) {
Patches currently in stable-queue which might be from michael.chan@xxxxxxxxxxxx are
queue-4.19/net-prevent-infinite-while-loop-in-skb_tx_hash.patch
