[Devel] [PATCH RHEL9 COMMIT] ms/net: neigh: don't call kfree_skb() under spin_lock_irqsave()

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-70.22.1.vz9.17.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh9-5.14.0-70.22.1.vz9.17.7
------>
commit 9fadd88f4f0b348b016b053da5fc72777988b761
Author: Yang Yingliang <yangyingliang at huawei.com>
Date:   Mon Aug 22 10:53:46 2022 +0800

    ms/net: neigh: don't call kfree_skb() under spin_lock_irqsave()
    
    It is not allowed to call kfree_skb() from hardware interrupt
    context or with interrupts being disabled. So add all skb to
    a tmp list, then free them after spin_unlock_irqrestore() at
    once.
    
    mFixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
    Suggested-by: Denis V. Lunev <den at openvz.org>
    Signed-off-by: Yang Yingliang <yangyingliang at huawei.com>
    Reviewed-by: Nikolay Aleksandrov <razor at blackwall.org>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    
    https://jira.sw.ru/browse/PSBM-141642
    https://lore.kernel.org/netdev/79784952-0d15-8a4a-aa8d-590bc243ab5e@virtuozzo.com/t/
    
    (cherry picked from ms commit d5485d9dd24e1d04e5509916515260186eb1455c)
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
    
    Feature: fix ms/net
---
 net/core/neighbour.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 4f7edf22c2fd..05568f6575ea 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -285,14 +285,17 @@ static int neigh_del_timer(struct neighbour *n)
 
 static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net)
 {
+	struct sk_buff_head tmp;
 	unsigned long flags;
 	struct sk_buff *skb;
 
+	skb_queue_head_init(&tmp);
 	spin_lock_irqsave(&list->lock, flags);
 	skb = skb_peek(list);
 	while (skb != NULL) {
 		struct sk_buff *skb_next = skb_peek_next(skb, list);
 		struct net_device *dev = skb->dev;
+
 		if (net == NULL || net_eq(dev_net(dev), net)) {
 			struct in_device *in_dev;
 
@@ -302,13 +305,16 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net)
 				in_dev->arp_parms->qlen--;
 			rcu_read_unlock();
 			__skb_unlink(skb, list);
-
-			dev_put(dev);
-			kfree_skb(skb);
+			__skb_queue_tail(&tmp, skb);
 		}
 		skb = skb_next;
 	}
 	spin_unlock_irqrestore(&list->lock, flags);
+
+	while ((skb = __skb_dequeue(&tmp))) {
+		dev_put(skb->dev);
+		kfree_skb(skb);
+	}
 }
 
 static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,