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[LTS 9.4] ndisc: use RCU protection in ndisc_alloc_skb() #546

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Merged
merged 3 commits into from
Sep 4, 2025
Merged

[LTS 9.4] ndisc: use RCU protection in ndisc_alloc_skb() #546

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82bfcc2
net: treat possible_net_t net pointer as an RCU one and add read_pnet…
pvts-mat Sep 2, 2025
e816125
net: add dev_net_rcu() helper
pvts-mat Sep 2, 2025
bf7d30e
ndisc: use RCU protection in ndisc_alloc_skb()
pvts-mat Sep 2, 2025
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6 changes: 6 additions & 0 deletions include/linux/netdevice.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2683,6 +2683,12 @@ struct net *dev_net(const struct net_device *dev)
return read_pnet(&dev->nd_net);
}

static inline
struct net *dev_net_rcu(const struct net_device *dev)
{
return read_pnet_rcu(&dev->nd_net);
}

static inline
void dev_net_set(struct net_device *dev, struct net *net)
{
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15 changes: 12 additions & 3 deletions include/net/net_namespace.h
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Original file line number Diff line number Diff line change
Expand Up @@ -350,21 +350,30 @@ static inline void put_net_track(struct net *net, netns_tracker *tracker)

typedef struct {
#ifdef CONFIG_NET_NS
struct net *net;
struct net __rcu *net;
#endif
} possible_net_t;

static inline void write_pnet(possible_net_t *pnet, struct net *net)
{
#ifdef CONFIG_NET_NS
pnet->net = net;
rcu_assign_pointer(pnet->net, net);
#endif
}

static inline struct net *read_pnet(const possible_net_t *pnet)
{
#ifdef CONFIG_NET_NS
return pnet->net;
return rcu_dereference_protected(pnet->net, true);
#else
return &init_net;
#endif
}

static inline struct net *read_pnet_rcu(const possible_net_t *pnet)
{
#ifdef CONFIG_NET_NS
return rcu_dereference(pnet->net);
#else
return &init_net;
#endif
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10 changes: 4 additions & 6 deletions net/ipv6/ndisc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -414,15 +414,11 @@ static struct sk_buff *ndisc_alloc_skb(struct net_device *dev,
{
int hlen = LL_RESERVED_SPACE(dev);
int tlen = dev->needed_tailroom;
struct sock *sk = dev_net(dev)->ipv6.ndisc_sk;
struct sk_buff *skb;

skb = alloc_skb(hlen + sizeof(struct ipv6hdr) + len + tlen, GFP_ATOMIC);
if (!skb) {
ND_PRINTK(0, err, "ndisc: %s failed to allocate an skb\n",
__func__);
if (!skb)
return NULL;
}

skb->protocol = htons(ETH_P_IPV6);
skb->dev = dev;
Expand All @@ -433,7 +429,9 @@ static struct sk_buff *ndisc_alloc_skb(struct net_device *dev,
/* Manually assign socket ownership as we avoid calling
* sock_alloc_send_pskb() to bypass wmem buffer limits
*/
skb_set_owner_w(skb, sk);
rcu_read_lock();
skb_set_owner_w(skb, dev_net_rcu(dev)->ipv6.ndisc_sk);
rcu_read_unlock();

return skb;
}
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