linux-kernel - [PATCH] inet: fix ip_mc_drop

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Date:	Mon, 08 Nov 2010 22:15:54 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	David Miller <davem@...emloft.net>
Cc:	paulmck@...ux.vnet.ibm.com, Miles Lane <miles.lane@...il.com>,
	ilpo.jarvinen@...sinki.fi, LKML <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH] inet: fix ip_mc_drop_socket()

Hmm, I believe I found the bug.

Thanks guys !

[PATCH] inet: fix ip_mc_drop_socket()

commit 8723e1b4ad9be4444 (inet: RCU changes in inetdev_by_index())
forgot one call site in ip_mc_drop_socket()

We should not decrease idev refcount after inetdev_by_index() call,
since refcount is not increased anymore.

Reported-by: Markus Trippelsdorf <markus@...ppelsdorf.de>
Reported-by: Miles Lane <miles.lane@...il.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/ipv4/igmp.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index c8877c6..3c53c2d 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -2306,10 +2306,8 @@ void ip_mc_drop_socket(struct sock *sk)
 
 		in_dev = inetdev_by_index(net, iml->multi.imr_ifindex);
 		(void) ip_mc_leave_src(sk, iml, in_dev);
-		if (in_dev != NULL) {
+		if (in_dev != NULL)
 			ip_mc_dec_group(in_dev, iml->multi.imr_multiaddr.s_addr);
-			in_dev_put(in_dev);
-		}
 		/* decrease mem now to avoid the memleak warning */
 		atomic_sub(sizeof(*iml), &sk->sk_omem_alloc);
 		call_rcu(&iml->rcu, ip_mc_socklist_reclaim);


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