linux-kernel - [PATCH AUTOSEL 6.0 17/77] genetlink: hold read cb_lock during iteration of genl_fam_idr in genl

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Date:   Sun,  9 Oct 2022 18:06:54 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jiri Pirko <jiri@...dia.com>,
        Vikas Gupta <vikas.gupta@...adcom.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>, davem@...emloft.net,
        edumazet@...gle.com, pabeni@...hat.com, nicolas.dichtel@...nd.com,
        gnault@...hat.com, johannes@...solutions.net,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 6.0 17/77] genetlink: hold read cb_lock during iteration of genl_fam_idr in genl_bind()

From: Jiri Pirko <jiri@...dia.com>

[ Upstream commit 8f1948bdcf2fb50e9092c0950c3c9ac591382101 ]

In genl_bind(), currently genl_lock and write cb_lock are taken
for iteration of genl_fam_idr and processing of static values
stored in struct genl_family. Take just read cb_lock for this task
as it is sufficient to guard the idr and the struct against
concurrent genl_register/unregister_family() calls.

This will allow to run genl command processing in genl_rcv() and
mnl_socket_setsockopt(.., NETLINK_ADD_MEMBERSHIP, ..) in parallel.

Reported-by: Vikas Gupta <vikas.gupta@...adcom.com>
Signed-off-by: Jiri Pirko <jiri@...dia.com>
Link: https://lore.kernel.org/r/20220825081940.1283335-1-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/netlink/genetlink.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 57010927e20a..76aed0571e3a 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1362,7 +1362,7 @@ static int genl_bind(struct net *net, int group)
 	unsigned int id;
 	int ret = 0;
 
-	genl_lock_all();
+	down_read(&cb_lock);
 
 	idr_for_each_entry(&genl_fam_idr, family, id) {
 		const struct genl_multicast_group *grp;
@@ -1383,7 +1383,7 @@ static int genl_bind(struct net *net, int group)
 		break;
 	}
 
-	genl_unlock_all();
+	up_read(&cb_lock);
 	return ret;
 }
 
-- 
2.35.1