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Miller" , Jakub Kicinski , , , CC: Joseph Huang Subject: [PATCH] bridge: Fix a deadlock when enabling multicast snooping Date: Tue, 1 Dec 2020 16:40:47 -0500 Message-ID: <20201201214047.128948-1-Joseph.Huang@garmin.com> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: OLAWPA-EXMB2.ad.garmin.com (10.5.144.24) To OLAWPA-EXMB4.ad.garmin.com (10.5.144.25) X-EOPAttributedMessage: 0 X-MS-Office365-Filtering-HT: Tenant X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 2f6863f8-ce1f-4ef7-7850-08d89641d21d X-MS-TrafficTypeDiagnostic: BYAPR04MB3784: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6430; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: AYGpeRrZi5vi6hYQAFCZf4oa0qv79Pl0vVpnSbTFzYe67yNoFmZL9/341wNm0J6iUob48kNsOzH23OkXOBPk7wCOn4dGKkUbom7xwBaiXWjcdYYvg9zndlKxXyexHZEufkuXnr0aAelWwBxWKnXKDPtd9cwRXx8CnBiQkzKJCUe+Z+mPGXMsIy0n5+dkOysCpVIWdPYXxphXydwRzOVLrQf2z6BMawf551YyeU2LeB9GHmjUcEzow7PvvNSiEQ1zP9V6bhc5rB8niggQpFHkN4T7xF5XEsjw43nTj/XTEvHgPwbQA/qzO+IqbLq0nm3qWIVhyrWERgVhrzvWMomqhVs5GKNFrUuEdmQlzo84VjPO1TRhMG4pEP2Am9Fv677vKmJtBr/2s+ZcRklieUcAaA== X-Forefront-Antispam-Report: CIP:204.77.163.244;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:edgetransport.garmin.com;PTR:extedge.garmin.com;CAT:NONE;SFS:(136003)(39850400004)(346002)(396003)(376002)(46966005)(7636003)(26005)(316002)(70586007)(426003)(110136005)(70206006)(8936002)(107886003)(336012)(5660300002)(83380400001)(2616005)(86362001)(8676002)(1076003)(4326008)(7696005)(186003)(36756003)(478600001)(47076004)(82740400003)(6666004)(356005)(82310400003)(2906002);DIR:OUT;SFP:1102; X-OriginatorOrg: garmin.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Dec 2020 21:41:11.3933 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2f6863f8-ce1f-4ef7-7850-08d89641d21d X-MS-Exchange-CrossTenant-Id: 38d0d425-ba52-4c0a-a03e-2a65c8e82e2d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=38d0d425-ba52-4c0a-a03e-2a65c8e82e2d;Ip=[204.77.163.244];Helo=[edgetransport.garmin.com] X-MS-Exchange-CrossTenant-AuthSource: BN7NAM10FT050.eop-nam10.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR04MB3784 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-12-01_11:2020-11-30,2020-12-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 impostorscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 spamscore=0 mlxscore=0 malwarescore=0 phishscore=0 suspectscore=0 bulkscore=0 mlxlogscore=982 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012010130 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When enabling multicast snooping, bridge module deadlocks on multicast_lock if 1) IPv6 is enabled, and 2) there is an existing querier on the same L2 network. The deadlock was caused by the following sequence: While holding the lock, br_multicast_open calls br_multicast_join_snoopers, which eventually causes IP stack to (attempt to) send out a Listener Report (in igmp6_join_group). Since the destination Ethernet address is a multicast address, br_dev_xmit feeds the packet back to the bridge via br_multicast_rcv, which in turn calls br_multicast_add_group, which then deadlocks on multicast_lock. The fix is to move the call br_multicast_join_snoopers outside of the critical section. This works since br_multicast_join_snoopers only deals with IP and does not modify any multicast data structures of the bridge, so there's no need to hold the lock. Fixes: 4effd28c1245 ("bridge: join all-snoopers multicast address") Signed-off-by: Joseph Huang --- net/bridge/br_device.c | 3 +++ net/bridge/br_multicast.c | 8 ++++---- net/bridge/br_private.h | 5 +++++ 3 files changed, 12 insertions(+), 4 deletions(-) diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index 7730c8f3cb53..8d3ec29d3875 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -177,6 +177,9 @@ static int br_dev_open(struct net_device *dev) br_stp_enable_bridge(br); br_multicast_open(br); + if (br_opt_get(br, BROPT_MULTICAST_ENABLED)) + br_multicast_join_snoopers(br); + return 0; } diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index eae898c3cff7..6c8d6b2eed91 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -3286,7 +3286,7 @@ static inline void br_ip6_multicast_join_snoopers(struct net_bridge *br) } #endif -static void br_multicast_join_snoopers(struct net_bridge *br) +void br_multicast_join_snoopers(struct net_bridge *br) { br_ip4_multicast_join_snoopers(br); br_ip6_multicast_join_snoopers(br); @@ -3336,9 +3336,6 @@ static void __br_multicast_open(struct net_bridge *br, void br_multicast_open(struct net_bridge *br) { - if (br_opt_get(br, BROPT_MULTICAST_ENABLED)) - br_multicast_join_snoopers(br); - __br_multicast_open(br, &br->ip4_own_query); #if IS_ENABLED(CONFIG_IPV6) __br_multicast_open(br, &br->ip6_own_query); @@ -3509,6 +3506,9 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val) unlock: spin_unlock_bh(&br->multicast_lock); + if (br_opt_get(br, BROPT_MULTICAST_ENABLED)) + br_multicast_join_snoopers(br); + return 0; } diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index 345118e35c42..7085dd747130 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -792,6 +792,7 @@ void br_multicast_del_port(struct net_bridge_port *port); void br_multicast_enable_port(struct net_bridge_port *port); void br_multicast_disable_port(struct net_bridge_port *port); void br_multicast_init(struct net_bridge *br); +void br_multicast_join_snoopers(struct net_bridge *br); void br_multicast_open(struct net_bridge *br); void br_multicast_stop(struct net_bridge *br); void br_multicast_dev_del(struct net_bridge *br); @@ -969,6 +970,10 @@ static inline void br_multicast_init(struct net_bridge *br) { } +static inline void br_multicast_join_snoopers(struct net_bridge *br) +{ +} + static inline void br_multicast_open(struct net_bridge *br) { } -- 2.29.2