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authorJakub Kicinski <jakub.kicinski@netronome.com>2018-02-12 21:35:31 -0800
committerDavid S. Miller <davem@davemloft.net>2018-02-14 14:12:55 -0500
commitac5b70198adc25c73fba28de4f78adcee8f6be0b (patch)
tree40a1ec058bf4f38d60a53bfe8f5f3e4bfa135c89 /net
parentd4014d8cc6dfa964e3e66df525de2384e3583018 (diff)
net: fix race on decreasing number of TX queues
netif_set_real_num_tx_queues() can be called when netdev is up. That usually happens when user requests change of number of channels/rings with ethtool -L. The procedure for changing the number of queues involves resetting the qdiscs and setting dev->num_tx_queues to the new value. When the new value is lower than the old one, extra care has to be taken to ensure ordering of accesses to the number of queues vs qdisc reset. Currently the queues are reset before new dev->num_tx_queues is assigned, leaving a window of time where packets can be enqueued onto the queues going down, leading to a likely crash in the drivers, since most drivers don't check if TX skbs are assigned to an active queue. Fixes: e6484930d7c7 ("net: allocate tx queues in register_netdevice") Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/dev.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index dda9d7b9a840..d4362befe7e2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2382,8 +2382,11 @@ EXPORT_SYMBOL(netdev_set_num_tc);
*/
int netif_set_real_num_tx_queues(struct net_device *dev, unsigned int txq)
{
+ bool disabling;
int rc;
+ disabling = txq < dev->real_num_tx_queues;
+
if (txq < 1 || txq > dev->num_tx_queues)
return -EINVAL;
@@ -2399,15 +2402,19 @@ int netif_set_real_num_tx_queues(struct net_device *dev, unsigned int txq)
if (dev->num_tc)
netif_setup_tc(dev, txq);
- if (txq < dev->real_num_tx_queues) {
+ dev->real_num_tx_queues = txq;
+
+ if (disabling) {
+ synchronize_net();
qdisc_reset_all_tx_gt(dev, txq);
#ifdef CONFIG_XPS
netif_reset_xps_queues_gt(dev, txq);
#endif
}
+ } else {
+ dev->real_num_tx_queues = txq;
}
- dev->real_num_tx_queues = txq;
return 0;
}
EXPORT_SYMBOL(netif_set_real_num_tx_queues);