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ipv4: snapshot dst.dev in ip_rt_send_redirect() and ip_rt_get_source()

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rt_flush_dev() can replace rt->dst.dev with blackhole_netdev while RCU
readers are running.  ip_rt_send_redirect() and ip_rt_get_source() both
read rt->dst.dev more than once and use the results in one operation.

If rt->dst.dev changes between those reads, the operation can use values
from two devices.  For example, ip_rt_send_redirect() can use in_dev from
the old device and the L3 master ifindex from blackhole_netdev.

Read rt->dst.dev once in these two functions and use the snapshot for the
later device accesses.

Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260708060537.17188-3-xuanqiang.luo@linux.dev
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Xuanqiang Luo
2026-07-21 11:45:53 +02:00
committed by Paolo Abeni
parent 1469773b24
commit 7804eaa057
1 changed files with 18 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/ipv4/route.c
+18 -13
View File
@@ -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);
}