From: Jakub Kicinski <kuba@xxxxxxxxxx>
[ Upstream commit 96e97bc07e90f175a8980a22827faf702ca4cb30 ]
napi_disable() makes sure to set the NAPI_STATE_NPSVC bit to prevent
netpoll from accessing rings before init is complete. However, the
same is not done for fresh napi instances in netif_napi_add(),
even though we expect NAPI instances to be added as disabled.
This causes crashes during driver reconfiguration (enabling XDP,
changing the channel count) - if there is any printk() after
netif_napi_add() but before napi_enable().
To ensure memory ordering is correct we need to use RCU accessors.
Reported-by: Rob Sherwood <rsher@xxxxxx>
Fixes: 2d8bff12699a ("netpoll: Close race condition between poll_one_napi and napi_disable")
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/dev.c | 3 ++-
net/core/netpoll.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5532,12 +5532,13 @@ void netif_napi_add(struct net_device *d
pr_err_once("netif_napi_add() called with weight %d on device %s\n",
weight, dev->name);
napi->weight = weight;
- list_add(&napi->dev_list, &dev->napi_list);
napi->dev = dev;
#ifdef CONFIG_NETPOLL
napi->poll_owner = -1;
#endif
set_bit(NAPI_STATE_SCHED, &napi->state);
+ set_bit(NAPI_STATE_NPSVC, &napi->state);
+ list_add_rcu(&napi->dev_list, &dev->napi_list);
napi_hash_add(napi);
}
EXPORT_SYMBOL(netif_napi_add);
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -179,7 +179,7 @@ static void poll_napi(struct net_device
struct napi_struct *napi;
int cpu = smp_processor_id();
- list_for_each_entry(napi, &dev->napi_list, dev_list) {
+ list_for_each_entry_rcu(napi, &dev->napi_list, dev_list) {
if (cmpxchg(&napi->poll_owner, -1, cpu) == -1) {
poll_one_napi(napi);
smp_store_release(&napi->poll_owner, -1);
