[PATCH net] net: igmp: increase size of mr_ifc_count

From: Eric Dumazet <edumazet@google.com>

Some arches support cmpxchg() on 4-byte and 8-byte only.
Increase mr_ifc_count width to 32bit to fix this problem.

Fixes: 4a2b285e7e10 ("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>
---
 include/linux/inetdevice.h | 2 +-
 net/ipv4/igmp.c            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index 53aa0343bf694cb817e00ff597b52ce046e29d2c..aaf4f1b4c277c4ad38e1f0742bb480d3bb003287 100644
--- 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
index a51360087b19845a28408c827032e08dabf99838..00576bae183d30518e376ad3846d4fe6025aaea7 100644
--- 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:

-- 
2.32.0.605.g8dce9f2422-goog

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Wed, 11 Aug 2021 12:57:15 -0700 you wrote:

From: Eric Dumazet <edumazet@google.com>

Some arches support cmpxchg() on 4-byte and 8-byte only.
Increase mr_ifc_count width to 32bit to fix this problem.

Fixes: 4a2b285e7e10 ("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>

[...]

Here is the summary with links:
  - [net] net: igmp: increase size of mr_ifc_count
    https://git.kernel.org/netdev/net/c/b69dd5b3780a

You are awesome, thank you!
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