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authorJakub Kicinski <jakub.kicinski@netronome.com>2018-02-12 21:35:31 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-11 16:21:31 +0100
commit106dc9648aa0db7b13f0c19f06b0786312a79c63 (patch)
tree4549561fda043d26fc842c89761472c03ddd3ef4 /net/core
parentc9a3046de72a9eb8fabe70ad3f1f0751152e9be6 (diff)
net: fix race on decreasing number of TX queues
[ Upstream commit ac5b70198adc25c73fba28de4f78adcee8f6be0b ] 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/core')
-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 8898618bf341..272f84ad16e0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2199,8 +2199,11 @@ EXPORT_SYMBOL(netif_set_xps_queue);
*/
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;
@@ -2216,15 +2219,19 @@ 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);