[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <1491474377.10124.57.camel@edumazet-glaptop3.roam.corp.google.com>
Date: Thu, 06 Apr 2017 03:26:17 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: Tushar Dave <tushar.n.dave@...cle.com>
Cc: davem@...emloft.net, edumazet@...gle.com, brouer@...hat.com,
netdev@...r.kernel.org, sowmini.varadhan@...cle.com
Subject: Re: [PATCH] netpoll: Check for skb->queue_mapping
On Wed, 2017-04-05 at 19:06 -0700, Tushar Dave wrote:
> Reducing real_num_tx_queues needs to be in sync with skb queue_mapping
> otherwise skbs with queue_mapping greater than real_num_tx_queues
> can be sent to the underlying driver and can result in kernel panic.
>
> One such event is running netconsole and enabling VF on the same
> device. Or running netconsole and changing number of tx queues via
> ethtool on same device.
>
> e.g.
>
> Signed-off-by: Tushar Dave <tushar.n.dave@...cle.com>
> ---
> net/core/netpoll.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> index 9424673..c572e49 100644
> --- a/net/core/netpoll.c
> +++ b/net/core/netpoll.c
> @@ -101,6 +101,7 @@ static void queue_process(struct work_struct *work)
> container_of(work, struct netpoll_info, tx_work.work);
> struct sk_buff *skb;
> unsigned long flags;
> + u16 q_index;
>
> while ((skb = skb_dequeue(&npinfo->txq))) {
> struct net_device *dev = skb->dev;
> @@ -117,6 +118,12 @@ static void queue_process(struct work_struct *work)
> HARD_TX_LOCK(dev, txq, smp_processor_id());
> if (netif_xmit_frozen_or_stopped(txq) ||
> netpoll_start_xmit(skb, dev, txq) != NETDEV_TX_OK) {
> + /* check if skb->queue_mapping has changed */
> + q_index = skb_get_queue_mapping(skb);
> + if (unlikely(q_index >= dev->real_num_tx_queues)) {
> + q_index = q_index % dev->real_num_tx_queues;
> + skb_set_queue_mapping(skb, q_index);
> + }
> skb_queue_head(&npinfo->txq, skb);
> HARD_TX_UNLOCK(dev, txq);
> local_irq_restore(flags);
Hi Thushar, thank you for working on this issue.
Where and when skb->queue_mapping has changed ?
It looks that the real problem is that dev->real_num_tx_queues has been
changed instead of skb->queue_mapping
So maybe the more correct change would be to cap skb->queue_mapping even
before getting skb_get_tx_queue() ?
Otherwise, even after your patch, we might still access an invalid queue
on the device ?
Something like the following :
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 9424673009c14e0fb288b8e4041dba596b37ee8d..16702d95f83ab884e605e3868cfef94615dcbc72 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -105,13 +105,20 @@ static void queue_process(struct work_struct *work)
while ((skb = skb_dequeue(&npinfo->txq))) {
struct net_device *dev = skb->dev;
struct netdev_queue *txq;
+ unsigned int q_index;
if (!netif_device_present(dev) || !netif_running(dev)) {
kfree_skb(skb);
continue;
}
- txq = skb_get_tx_queue(dev, skb);
+ /* check if skb->queue_mapping is still valid */
+ q_index = skb_get_queue_mapping(skb);
+ if (unlikely(q_index >= dev->real_num_tx_queues)) {
+ q_index = q_index % dev->real_num_tx_queues;
+ skb_set_queue_mapping(skb, q_index);
+ }
+ txq = netdev_get_tx_queue(dev, q_index);
local_irq_save(flags);
HARD_TX_LOCK(dev, txq, smp_processor_id());
Powered by blists - more mailing lists