A netadmin in a user+net namespace can create many IPv6 multicast routing tables with MRT6_TABLE. Each unseen id allocates an mr_table, links it into mr6_tables, and leaves it until netns teardown. Those objects were not charged to memcg, so the host unreclaimable slab grows with the table count. Account mr_table allocations with GFP_KERNEL_ACCOUNT and mark the IPv4/IPv6 MFC caches SLAB_ACCOUNT. This matches the established handling of IP addresses, routes and alternate interface names. The first unaccounted IPv6 heap table appeared in commit 4e16880cb422 ("netns: ip6mr: dynamically allocates vif6_table"), which replaced a static vif6_table[] with kcalloc(..., GFP_KERNEL). Commit 6bd521433942 ("ipv6: ip6mr: move mroute data into seperate structure") only wrapped that already-heap state into mr6_table. Commit d1db275dd3f6 ("ipv6: ip6mr: support multiple tables") only expanded the table count from 1 to N. IPv6 MFC entries were already unaccounted from commit 7bc570c8b4f7 ("[IPV6] MROUTE: Support multicast forwarding."); IPv4 ip_mrt_cache is older still. Fixes: 4e16880cb422 ("netns: ip6mr: dynamically allocates vif6_table") Cc: stable@vger.kernel.org Reported-by: Vega Assisted-by: LLM Signed-off-by: Zihan Xi --- changes in v3: - Drop the table lifetime / unpublished-alloc / empty-reclaim approach from v2. - Charge mr_table allocations with GFP_KERNEL_ACCOUNT and mark the IPv4/IPv6 MFC caches SLAB_ACCOUNT, as suggested by Ido Schimmel. - Point Fixes: at 4e16880cb422, the first GFP_KERNEL IPv6 heap vif6_table. 6bd521433942 only wrapped that already-heap state; d1db275dd3f6 only expanded the table count from 1 to N. - Cover: unfixed evidence is Slab/SUnreclaim growth with RET:0, not a host OOM. The memcg OOM log is from the patched kernel under 64M memory.max using poc.static. - v2 Link: https://lore.kernel.org/all/cover.1788622674.git.zihanx@nebusec.ai/ changes in v2: - Drop the shared mr_table refcount / list_del_rcu path that broke the ipmr forwarding selftest. - Limit the v2 approach to net/ipv6/ip6mr.c. - v1 Link: https://lore.kernel.org/all/cover.1784795838.git.zihanx@nebusec.ai/ net/ipv4/ipmr.c | 3 ++- net/ipv4/ipmr_base.c | 2 +- net/ipv6/ip6mr.c | 2 +- 3 files changed, 4 insertions(+), 3 deletions(-) diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c index e5f2b1c6150d2..b9c544d48c452 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 867b24beded11..a0ec6d19a237f 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 3f2ed9b77deb5..9d8116b5edb17 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; base-commit: 641d03105cc0d2437e32fdeec164f91a4ccef6c4 -- 2.43.0