[PATCH 5.4 30/87] igmp: Fix data-races around sysctl_igmp_llm_reports.

Greg Kroah-Hartman
2022-07-27T16:39:34Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit f6da2267e71106474fbc0943dc24928b9cb79119 ]

While reading sysctl_igmp_llm_reports, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

This test can be packed into a helper, so such changes will be in the
follow-up series after net is merged into net-next.

if (ipv4_is_local_multicast(pmc->multiaddr) &&
!READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))

Fixes: df2cf4a78e48 ("IGMP: Inhibit reports for local multicast groups")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/igmp.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index cac2fdd08df0..7cd444d75c3d 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -469,7 +469,8 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc,

if (pmc->multiaddr == IGMP_ALL_HOSTS)
return skb;
- if (ipv4_is_local_multicast(pmc->multiaddr) && !net->ipv4.sysctl_igmp_llm_reports)
+ if (ipv4_is_local_multicast(pmc->multiaddr) &&
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
return skb;

mtu = READ_ONCE(dev->mtu);
@@ -595,7 +596,7 @@ static int igmpv3_send_report(struct in_device *in_dev, struct ip_mc_list *pmc)
if (pmc->multiaddr == IGMP_ALL_HOSTS)
continue;
if (ipv4_is_local_multicast(pmc->multiaddr) &&
- !net->ipv4.sysctl_igmp_llm_reports)
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
continue;
spin_lock_bh(&pmc->lock);
if (pmc->sfcount[MCAST_EXCLUDE])
@@ -738,7 +739,8 @@ static int igmp_send_report(struct in_device *in_dev, struct ip_mc_list *pmc,
if (type == IGMPV3_HOST_MEMBERSHIP_REPORT)
return igmpv3_send_report(in_dev, pmc);

- if (ipv4_is_local_multicast(group) && !net->ipv4.sysctl_igmp_llm_reports)
+ if (ipv4_is_local_multicast(group) &&
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
return 0;

if (type == IGMP_HOST_LEAVE_MESSAGE)
@@ -922,7 +924,8 @@ static bool igmp_heard_report(struct in_device *in_dev, __be32 group)

if (group == IGMP_ALL_HOSTS)
return false;
- if (ipv4_is_local_multicast(group) && !net->ipv4.sysctl_igmp_llm_reports)
+ if (ipv4_is_local_multicast(group) &&
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
return false;

rcu_read_lock();
@@ -1047,7 +1050,7 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
if (im->multiaddr == IGMP_ALL_HOSTS)
continue;
if (ipv4_is_local_multicast(im->multiaddr) &&
- !net->ipv4.sysctl_igmp_llm_reports)
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
continue;
spin_lock_bh(&im->lock);
if (im->tm_running)
@@ -1298,7 +1301,8 @@ static void __igmp_group_dropped(struct ip_mc_list *im, gfp_t gfp)
#ifdef CONFIG_IP_MULTICAST
if (im->multiaddr == IGMP_ALL_HOSTS)
return;
- if (ipv4_is_local_multicast(im->multiaddr) && !net->ipv4.sysctl_igmp_llm_reports)
+ if (ipv4_is_local_multicast(im->multiaddr) &&
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
return;

reporter = im->reporter;
@@ -1340,7 +1344,8 @@ static void igmp_group_added(struct ip_mc_list *im)
#ifdef CONFIG_IP_MULTICAST
if (im->multiaddr == IGMP_ALL_HOSTS)
return;
- if (ipv4_is_local_multicast(im->multiaddr) && !net->ipv4.sysctl_igmp_llm_reports)
+ if (ipv4_is_local_multicast(im->multiaddr) &&
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
return;

if (in_dev->dead)
@@ -1644,7 +1649,7 @@ static void ip_mc_rejoin_groups(struct in_device *in_dev)
if (im->multiaddr == IGMP_ALL_HOSTS)
continue;
if (ipv4_is_local_multicast(im->multiaddr) &&
- !net->ipv4.sysctl_igmp_llm_reports)
+ !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))
continue;

/* a failover is happening and switches
--
2.35.1