ipv4: igmp: annotate data-races around idev->mr_maxdelay

edumazet · kuba-moo · commit e4faaf65a75f · 2026-01-25T14:45:14.000-08:00
idev->mr_maxdelay is read and written locklessly, add READ_ONCE()/WRITE_ONCE() annotations. While we are at it, make this field an u32. Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: David Ahern <dsahern@kernel.org> Link: https://patch.msgid.link/20260122172247.2429403-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
@@ -38,11 +38,11 @@ struct in_device {
 	struct ip_mc_list	*mc_tomb;
 	unsigned long		mr_v1_seen;
 	unsigned long		mr_v2_seen;
-	unsigned long		mr_maxdelay;
 	unsigned long		mr_qi;		/* Query Interval */
 	unsigned long		mr_qri;		/* Query Response Interval */
 	unsigned char		mr_qrv;		/* Query Robustness Variable */
 	unsigned char		mr_gq_running;
+	u32			mr_maxdelay;
 	u32			mr_ifc_count;
 	struct timer_list	mr_gq_timer;	/* general query timer */
 	struct timer_list	mr_ifc_timer;	/* interface change timer */
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
@@ -227,7 +227,7 @@ static void igmp_start_timer(struct ip_mc_list *im, int max_delay)
 
 static void igmp_gq_start_timer(struct in_device *in_dev)
 {
-	int tv = get_random_u32_below(in_dev->mr_maxdelay);
+	int tv = get_random_u32_below(READ_ONCE(in_dev->mr_maxdelay));
 	unsigned long exp = jiffies + tv + 2;
 
 	if (in_dev->mr_gq_running &&
@@ -1009,7 +1009,7 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
 		max_delay = IGMPV3_MRC(ih3->code)*(HZ/IGMP_TIMER_SCALE);
 		if (!max_delay)
 			max_delay = 1;	/* can't mod w/ 0 */
-		in_dev->mr_maxdelay = max_delay;
+		WRITE_ONCE(in_dev->mr_maxdelay, max_delay);
 
 		/* RFC3376, 4.1.6. QRV and 4.1.7. QQIC, when the most recently
 		 * received value was zero, use the default or statically
