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ipmr: Convert ipmr_rtm_getroute() to RCU.

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ipmr_rtm_getroute() calls __ipmr_get_table(), ipmr_cache_find(),
and ipmr_fill_mroute().

The table is not removed until netns dismantle, and net->ipv4.mr_tables
is managed with RCU list API, so __ipmr_get_table() is safe under RCU.

struct mfc_cache is freed by mr_cache_put() after RCU grace period,
so we can use ipmr_cache_find() under RCU.  rcu_read_lock() around
it was just to avoid lockdep splat for rhl_for_each_entry_rcu().

ipmr_fill_mroute() calls mr_fill_mroute(), which properly uses RCU.

Let's drop RTNL for ipmr_rtm_getroute() and use RCU instead.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260228221800.1082070-6-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2026-03-02 18:49:40 -08:00
committed by Jakub Kicinski
parent 2bd6c9d600
commit 295a17b3ea
2 changed files with 25 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/ipv4/ipmr.c
+23 -21
View File
@@ -2680,9 +2680,9 @@ static int ipmr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
{
struct net *net = sock_net(in_skb->sk);
struct nlattr *tb[RTA_MAX + 1];
struct sk_buff *skb = NULL;
struct mfc_cache *cache;
struct mr_table *mrt;
struct sk_buff *skb;
__be32 src, grp;
u32 tableid;
int err;
@@ -2695,39 +2695,40 @@ static int ipmr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
grp = nla_get_in_addr_default(tb[RTA_DST], 0);
tableid = nla_get_u32_default(tb[RTA_TABLE], 0);
mrt = __ipmr_get_table(net, tableid ? tableid : RT_TABLE_DEFAULT);
if (!mrt) {
err = -ENOENT;
goto errout_free;
}
/* entries are added/deleted only under RTNL */
rcu_read_lock();
cache = ipmr_cache_find(mrt, src, grp);
rcu_read_unlock();
if (!cache) {
err = -ENOENT;
goto errout_free;
}
skb = nlmsg_new(mroute_msgsize(false), GFP_KERNEL);
if (!skb) {
err = -ENOBUFS;
goto errout_free;
goto errout;
}
rcu_read_lock();
mrt = __ipmr_get_table(net, tableid ? tableid : RT_TABLE_DEFAULT);
if (!mrt) {
err = -ENOENT;
goto errout_unlock;
}
cache = ipmr_cache_find(mrt, src, grp);
if (!cache) {
err = -ENOENT;
goto errout_unlock;
}
err = ipmr_fill_mroute(mrt, skb, NETLINK_CB(in_skb).portid,
nlh->nlmsg_seq, cache,
RTM_NEWROUTE, 0);
if (err < 0)
goto errout_free;
goto errout_unlock;
rcu_read_unlock();
err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
errout:
return err;
errout_free:
errout_unlock:
rcu_read_unlock();
kfree_skb(skb);
goto errout;
}
@@ -3297,7 +3298,8 @@ static const struct rtnl_msg_handler ipmr_rtnl_msg_handlers[] __initconst = {
{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_DELROUTE,
.doit = ipmr_rtm_route},
{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_GETROUTE,
.doit = ipmr_rtm_getroute, .dumpit = ipmr_rtm_dumproute},
.doit = ipmr_rtm_getroute, .dumpit = ipmr_rtm_dumproute,
.flags = RTNL_FLAG_DOIT_UNLOCKED},
};
int __init ip_mr_init(void)
net/ipv4/ipmr_base.c
+2 -2
View File
@@ -223,7 +223,7 @@ int mr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
rcu_read_lock();
vif_dev = rcu_dereference(mrt->vif_table[c->mfc_parent].dev);
if (vif_dev && nla_put_u32(skb, RTA_IIF, vif_dev->ifindex) < 0) {
if (vif_dev && nla_put_u32(skb, RTA_IIF, READ_ONCE(vif_dev->ifindex)) < 0) {
rcu_read_unlock();
return -EMSGSIZE;
}
@@ -252,7 +252,7 @@ int mr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
nhp->rtnh_flags = 0;
nhp->rtnh_hops = c->mfc_un.res.ttls[ct];
nhp->rtnh_ifindex = vif_dev->ifindex;
nhp->rtnh_ifindex = READ_ONCE(vif_dev->ifindex);
nhp->rtnh_len = sizeof(*nhp);
}
}