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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Patrick McHardy , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Vega Subject: Re: [PATCH net v2 1/1] ipv6: ip6mr: fix mr_table leak from MRT6_TABLE Message-ID: <20260906181910.GA455897@shredder> References: <5fc14a8ba754126b6897939e11154167281d4c5f.1788622674.git.zihanx@nebusec.ai> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5fc14a8ba754126b6897939e11154167281d4c5f.1788622674.git.zihanx@nebusec.ai> X-ClientProxiedBy: FR4P281CA0229.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:e9::7) To PH0PR12MB7957.namprd12.prod.outlook.com (2603:10b6:510:281::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR12MB7957:EE_|LV8PR12MB9405:EE_ X-MS-Office365-Filtering-Correlation-Id: 17d14c14-756e-4213-1852-08df0c435fbb X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|7416014|366016|1800799024|376014|10067099003|22082099003|18002099003|11063799006|56012099006|4143699003; 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The new mr_table is linked into mr6_tables and is only > destroyed when the net namespace goes away. > > A raw ICMPv6 socket with CAP_NET_ADMIN can therefore loop > MRT6_TABLE(fresh id) without MRT6_INIT, close the socket, and still > leave the tables allocated. Repeating this grows unreclaimable slab > until the machine OOMs. Isn't the established way to deal with this sort of issue to simply account for the memory and assume that the admin put some kind of a memory limit on the container? See for example commit 6126891c6d4f ("memcg: enable accounting for IP address and routing-related objects") and commit 5d26cff5bdbe ("net: account alternate interface name memory"). This diff [1] accounts for the memory of both the multicast tables and the multicast routes. With your C reproducer and this diff I get: # echo +memory > /sys/fs/cgroup/cgroup.subtree_control # mkdir /sys/fs/cgroup/mrtest # echo 64M > /sys/fs/cgroup/mrtest/memory.max # echo $$ > /sys/fs/cgroup/mrtest/cgroup.procs # unshare -Urn ./mrt_poc allocated=1 current_table=1 maxrss_kb=1788 allocated=10001 current_table=10001 maxrss_kb=1788 Killed bash # dmesg | tail -1 [ 63.360047] Memory cgroup out of memory: Killed process 297 (mrt_poc) total-vm:2424kB, anon-rss:92kB, file-rss:1448kB, shmem-rss:0kB, UID:0 pgtables:44kB oom_score_adj:0 [1] diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c index e5f2b1c6150d..b9c544d48c45 100644 --- a/net/ipv4/ipmr.c +++ b/net/ipv4/ipmr.c @@ -3376,7 +3376,8 @@ int __init ip_mr_init(void) { int err; - mrt_cachep = KMEM_CACHE(mfc_cache, SLAB_HWCACHE_ALIGN | SLAB_PANIC); + mrt_cachep = KMEM_CACHE(mfc_cache, + SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT); err = register_pernet_subsys(&ipmr_net_ops); if (err) diff --git a/net/ipv4/ipmr_base.c b/net/ipv4/ipmr_base.c index 867b24beded1..a0ec6d19a237 100644 --- a/net/ipv4/ipmr_base.c +++ b/net/ipv4/ipmr_base.c @@ -52,7 +52,7 @@ mr_table_alloc(struct net *net, u32 id, struct mr_table *mrt; int err; - mrt = kzalloc_obj(*mrt); + mrt = kzalloc_obj(*mrt, GFP_KERNEL_ACCOUNT); if (!mrt) return ERR_PTR(-ENOMEM); mrt->id = id; diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c index 3f2ed9b77deb..9d8116b5edb1 100644 --- a/net/ipv6/ip6mr.c +++ b/net/ipv6/ip6mr.c @@ -1427,7 +1427,7 @@ int __init ip6_mr_init(void) { int err; - mrt_cachep = KMEM_CACHE(mfc6_cache, SLAB_HWCACHE_ALIGN); + mrt_cachep = KMEM_CACHE(mfc6_cache, SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT); if (!mrt_cachep) return -ENOMEM;