[PATCH net] ipv4: igmp: annotate data-races in igmp_heard_query()

[PATCH net] ipv4: igmp: annotate data-races in igmp_heard_query()

[Eric Dumazet]

Multiple cpus can run igmp_heard_query() concurrently.

Add missing READ_ONCE()/WRITE_ONCE() over following in_dev fields.

- mr_qrv
- mr_qi
- mr_qri
- mr_v1_seen
- mr_v2_seen

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+ae9a171f239b14485310@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/69f38675.050a0220.3cbe47.0002.GAE@google.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/igmp.c | 58 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 36 insertions(+), 22 deletions(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index a674fb44ec25baf963dbaf9e72ccc45980b858b6..a9ad39064f3bb7fcfaace52448473f0425b2fa07 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -122,16 +122,29 @@
  * contradict to specs provided this delay is small enough.
  */
 
-#define IGMP_V1_SEEN(in_dev) \
-	(IPV4_DEVCONF_ALL_RO(dev_net(in_dev->dev), FORCE_IGMP_VERSION) == 1 || \
-	 IN_DEV_CONF_GET((in_dev), FORCE_IGMP_VERSION) == 1 || \
-	 ((in_dev)->mr_v1_seen && \
-	  time_before(jiffies, (in_dev)->mr_v1_seen)))
-#define IGMP_V2_SEEN(in_dev) \
-	(IPV4_DEVCONF_ALL_RO(dev_net(in_dev->dev), FORCE_IGMP_VERSION) == 2 || \
-	 IN_DEV_CONF_GET((in_dev), FORCE_IGMP_VERSION) == 2 || \
-	 ((in_dev)->mr_v2_seen && \
-	  time_before(jiffies, (in_dev)->mr_v2_seen)))
+static bool IGMP_V1_SEEN(const struct in_device *in_dev)
+{
+	unsigned long seen;
+
+	if (IPV4_DEVCONF_ALL_RO(dev_net(in_dev->dev), FORCE_IGMP_VERSION) == 1)
+		return true;
+	if (IN_DEV_CONF_GET((in_dev), FORCE_IGMP_VERSION) == 1)
+		return true;
+	seen = READ_ONCE(in_dev->mr_v1_seen);
+	return seen && time_before(jiffies, seen);
+}
+
+static bool IGMP_V2_SEEN(const struct in_device *in_dev)
+{
+	unsigned long seen;
+
+	if (IPV4_DEVCONF_ALL_RO(dev_net(in_dev->dev), FORCE_IGMP_VERSION) == 2)
+		return true;
+	if (IN_DEV_CONF_GET((in_dev), FORCE_IGMP_VERSION) == 2)
+		return true;
+	seen = READ_ONCE(in_dev->mr_v2_seen);
+	return seen && time_before(jiffies, seen);
+}
 
 static int unsolicited_report_interval(struct in_device *in_dev)
 {
@@ -954,23 +967,21 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
 	int			max_delay;
 	int			mark = 0;
 	struct net		*net = dev_net(in_dev->dev);
-
+	unsigned long seen;
 
 	if (len == 8) {
+		seen = jiffies + READ_ONCE(in_dev->mr_qrv) * READ_ONCE(in_dev->mr_qi) +
+		       READ_ONCE(in_dev->mr_qri);
 		if (ih->code == 0) {
 			/* Alas, old v1 router presents here. */
 
 			max_delay = IGMP_QUERY_RESPONSE_INTERVAL;
-			in_dev->mr_v1_seen = jiffies +
-				(in_dev->mr_qrv * in_dev->mr_qi) +
-				in_dev->mr_qri;
+			WRITE_ONCE(in_dev->mr_v1_seen, seen);
 			group = 0;
 		} else {
 			/* v2 router present */
 			max_delay = ih->code*(HZ/IGMP_TIMER_SCALE);
-			in_dev->mr_v2_seen = jiffies +
-				(in_dev->mr_qrv * in_dev->mr_qi) +
-				in_dev->mr_qri;
+			WRITE_ONCE(in_dev->mr_v2_seen, seen);
 		}
 		/* cancel the interface change timer */
 		WRITE_ONCE(in_dev->mr_ifc_count, 0);
@@ -995,6 +1006,8 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
 		if (!max_delay)
 			max_delay = 1;	/* can't mod w/ 0 */
 	} else { /* v3 */
+		unsigned long mr_qi;
+
 		if (!pskb_may_pull(skb, sizeof(struct igmpv3_query)))
 			return true;
 
@@ -1015,15 +1028,16 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
 		 * received value was zero, use the default or statically
 		 * configured value.
 		 */
-		in_dev->mr_qrv = ih3->qrv ?: READ_ONCE(net->ipv4.sysctl_igmp_qrv);
-		in_dev->mr_qi = IGMPV3_QQIC(ih3->qqic)*HZ ?: IGMP_QUERY_INTERVAL;
-
+		WRITE_ONCE(in_dev->mr_qrv,
+			   ih3->qrv ?: READ_ONCE(net->ipv4.sysctl_igmp_qrv));
+		mr_qi = IGMPV3_QQIC(ih3->qqic)*HZ ?: IGMP_QUERY_INTERVAL;
+		WRITE_ONCE(in_dev->mr_qi, mr_qi);
 		/* RFC3376, 8.3. Query Response Interval:
 		 * The number of seconds represented by the [Query Response
 		 * Interval] must be less than the [Query Interval].
 		 */
-		if (in_dev->mr_qri >= in_dev->mr_qi)
-			in_dev->mr_qri = (in_dev->mr_qi/HZ - 1)*HZ;
+		if (READ_ONCE(in_dev->mr_qri) >= mr_qi)
+			WRITE_ONCE(in_dev->mr_qri, (mr_qi/HZ - 1) * HZ);
 
 		if (!group) { /* general query */
 			if (ih3->nsrcs)
-- 
2.54.0.545.g6539524ca2-goog

Re: [PATCH net] ipv4: igmp: annotate data-races in igmp_heard_query()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 30 Apr 2026 16:48:36 +0000 you wrote:
> Multiple cpus can run igmp_heard_query() concurrently.
> 
> Add missing READ_ONCE()/WRITE_ONCE() over following in_dev fields.
> 
> - mr_qrv
> - mr_qi
> - mr_qri
> - mr_v1_seen
> - mr_v2_seen
> 
> [...]

Here is the summary with links:
  - [net] ipv4: igmp: annotate data-races in igmp_heard_query()
    https://git.kernel.org/netdev/net/c/c6bebaa744f7

You are awesome, thank you!
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