[PATCH v3 net-next 03/15] ip6mr: Annotate access to mrt->mroute_do_{pim,assert,wrvifwhole}.

Kuniyuki Iwashima
2026-04-07T21:20:09Z

These fields in struct mr_table are updated in ip6_mroute_setsockopt()
under RTNL:

* mroute_do_pim
* mroute_do_assert
* mroute_do_wrvifwhole

However, ip6_mroute_getsockopt() does not hold RTNL and read the first
two fields locklessly, and ip6_mr_forward() reads all the three under
RCU.

Let's use WRITE_ONCE() and READ_ONCE() for them.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
net/ipv6/ip6mr.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 5755244e226c..5d368ee39b28 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1783,7 +1783,7 @@ int ip6_mroute_setsockopt(struct sock *sk, int optname, sockptr_t optval,
return -EINVAL;
if (copy_from_sockptr(&v, optval, sizeof(v)))
return -EFAULT;
- mrt->mroute_do_assert = v;
+ WRITE_ONCE(mrt->mroute_do_assert, v);
return 0;
}

@@ -1803,9 +1803,9 @@ int ip6_mroute_setsockopt(struct sock *sk, int optname, sockptr_t optval,
rtnl_lock();
ret = 0;
if (v != mrt->mroute_do_pim) {
- mrt->mroute_do_pim = v;
- mrt->mroute_do_assert = v;
- mrt->mroute_do_wrvifwhole = do_wrmifwhole;
+ WRITE_ONCE(mrt->mroute_do_pim, v);
+ WRITE_ONCE(mrt->mroute_do_assert, v);
+ WRITE_ONCE(mrt->mroute_do_wrvifwhole, do_wrmifwhole);
}
rtnl_unlock();
return ret;
@@ -1873,11 +1873,11 @@ int ip6_mroute_getsockopt(struct sock *sk, int optname, sockptr_t optval,
break;
#ifdef CONFIG_IPV6_PIMSM_V2
case MRT6_PIM:
- val = mrt->mroute_do_pim;
+ val = READ_ONCE(mrt->mroute_do_pim);
break;
#endif
case MRT6_ASSERT:
- val = mrt->mroute_do_assert;
+ val = READ_ONCE(mrt->mroute_do_assert);
break;
default:
return -ENOPROTOOPT;
@@ -2180,20 +2180,20 @@ static void ip6_mr_forward(struct net *net, struct mr_table *mrt,
if (rcu_access_pointer(mrt->vif_table[vif].dev) != dev) {
atomic_long_inc(&c->_c.mfc_un.res.wrong_if);

- if (true_vifi >= 0 && mrt->mroute_do_assert &&
+ if (true_vifi >= 0 && READ_ONCE(mrt->mroute_do_assert) &&
/* pimsm uses asserts, when switching from RPT to SPT,
so that we cannot check that packet arrived on an oif.
It is bad, but otherwise we would need to move pretty
large chunk of pimd to kernel. Ough... --ANK
*/
- (mrt->mroute_do_pim ||
+ (READ_ONCE(mrt->mroute_do_pim) ||
c->_c.mfc_un.res.ttls[true_vifi] < 255) &&
time_after(jiffies,
c->_c.mfc_un.res.last_assert +
MFC_ASSERT_THRESH)) {
c->_c.mfc_un.res.last_assert = jiffies;
ip6mr_cache_report(mrt, skb, true_vifi, MRT6MSG_WRONGMIF);
- if (mrt->mroute_do_wrvifwhole)
+ if (READ_ONCE(mrt->mroute_do_wrvifwhole))
ip6mr_cache_report(mrt, skb, true_vifi,
MRT6MSG_WRMIFWHOLE);
}
--
2.53.0.1213.gd9a14994de-goog