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Merge branch 'ipv4-update-rt_flush_dev-and-two-dst-dev-readers'

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Xuanqiang Luo says:

====================
ipv4: update rt_flush_dev() and two dst.dev readers

From: Xuanqiang Luo <xuanqiang.luo@linux.dev>

Patch 1 makes the rt_flush_dev() write to rt->dst.dev use
rcu_assign_pointer(), matching the existing dst_dev_rcu() readers.

Patch 2 makes ip_rt_send_redirect() and ip_rt_get_source() use one
dst.dev snapshot throughout each operation, so a concurrent rt_flush_dev()
update cannot make them use values from two devices.

v2: https://lore.kernel.org/lkml/20260701032434.17500-1-xuanqiang.luo@linux.dev/
v1: https://lore.kernel.org/all/20260630094250.29386-1-xuanqiang.luo@linux.dev/
====================

Link: https://patch.msgid.link/20260708060537.17188-1-xuanqiang.luo@linux.dev
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Paolo Abeni
2026-07-21 11:45:54 +02:00
parent b9ecdfda4d 7804eaa057
commit abc435224e
1 changed files with 19 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
net/ipv4/route.c
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@@ -874,21 +874,23 @@ void ip_rt_send_redirect(struct sk_buff *skb)
{
struct rtable *rt = skb_rtable(skb);
struct in_device *in_dev;
struct net_device *dev;
struct inet_peer *peer;
struct net *net;
int log_martians;
struct net *net;
int vif;
rcu_read_lock();
in_dev = __in_dev_get_rcu(rt->dst.dev);
dev = dst_dev_rcu(&rt->dst);
in_dev = __in_dev_get_rcu(dev);
if (!in_dev || !IN_DEV_TX_REDIRECTS(in_dev)) {
rcu_read_unlock();
return;
}
log_martians = IN_DEV_LOG_MARTIANS(in_dev);
vif = l3mdev_master_ifindex_rcu(rt->dst.dev);
vif = l3mdev_master_ifindex_rcu(dev);
net = dev_net(rt->dst.dev);
net = dev_net_rcu(dev);
peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr, vif);
if (!peer) {
rcu_read_unlock();
@@ -1287,29 +1289,32 @@ void ip_rt_get_source(u8 *addr, struct sk_buff *skb, struct rtable *rt)
{
__be32 src;
if (rt_is_output_route(rt))
rcu_read_lock();
if (rt_is_output_route(rt)) {
src = ip_hdr(skb)->saddr;
else {
struct fib_result res;
} else {
struct net_device *dev = dst_dev_rcu(&rt->dst);
struct net *net = dev_net_rcu(dev);
struct iphdr *iph = ip_hdr(skb);
struct fib_result res;
struct flowi4 fl4 = {
.daddr = iph->daddr,
.saddr = iph->saddr,
.flowi4_dscp = ip4h_dscp(iph),
.flowi4_oif = rt->dst.dev->ifindex,
.flowi4_oif = dev->ifindex,
.flowi4_iif = skb->dev->ifindex,
.flowi4_mark = skb->mark,
};
rcu_read_lock();
if (fib_lookup(dev_net(rt->dst.dev), &fl4, &res, 0) == 0)
src = fib_result_prefsrc(dev_net(rt->dst.dev), &res);
if (fib_lookup(net, &fl4, &res, 0) == 0)
src = fib_result_prefsrc(net, &res);
else
src = inet_select_addr(rt->dst.dev,
src = inet_select_addr(dev,
rt_nexthop(rt, iph->daddr),
RT_SCOPE_UNIVERSE);
rcu_read_unlock();
}
rcu_read_unlock();
memcpy(addr, &src, 4);
}
@@ -1565,7 +1570,7 @@ void rt_flush_dev(struct net_device *dev)
list_for_each_entry_safe(rt, safe, &ul->head, dst.rt_uncached) {
if (rt->dst.dev != dev)
continue;
rt->dst.dev = blackhole_netdev;
rcu_assign_pointer(rt->dst.dev_rcu, blackhole_netdev);
netdev_ref_replace(dev, blackhole_netdev,
&rt->dst.dev_tracker, GFP_ATOMIC);
list_del_init(&rt->dst.rt_uncached);