net: igmp: increase size of mr_ifc_count

edumazet · kuba-moo · commit b69dd5b3780a · 2021-08-11T15:54:10.000-07:00
Some arches support cmpxchg() on 4-byte and 8-byte only. Increase mr_ifc_count width to 32bit to fix this problem. Fixes: 4a2b285 ("net: igmp: fix data-race in igmp_ifc_timer_expire()") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/r/20210811195715.3684218-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
@@ -41,7 +41,7 @@ struct in_device {
 	unsigned long		mr_qri;		/* Query Response Interval */
 	unsigned char		mr_qrv;		/* Query Robustness Variable */
 	unsigned char		mr_gq_running;
-	unsigned char		mr_ifc_count;
+	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
@@ -803,7 +803,7 @@ static void igmp_gq_timer_expire(struct timer_list *t)
 static void igmp_ifc_timer_expire(struct timer_list *t)
 {
 	struct in_device *in_dev = from_timer(in_dev, t, mr_ifc_timer);
-	u8 mr_ifc_count;
+	u32 mr_ifc_count;
 
 	igmpv3_send_cr(in_dev);
 restart:

Original file line number	Diff line number	Diff line change
`@@ -803,7 +803,7 @@ static void igmp_gq_timer_expire(struct timer_list *t)`
`803`	`803`	`static void igmp_ifc_timer_expire(struct timer_list *t)`
`804`	`804`	`{`
`805`	`805`	`struct in_device *in_dev = from_timer(in_dev, t, mr_ifc_timer);`
`806`		`- u8 mr_ifc_count;`
	`806`	`+ u32 mr_ifc_count;`
`807`	`807`
`808`	`808`	`igmpv3_send_cr(in_dev);`
`809`	`809`	`restart:`