From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Zihan Xi <zihanx@nebusec.ai>,
	Vega <vega@nebusec.ai>,
	Ido Schimmel <idosch@nvidia.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10.y] ipmr: account multicast table and route memory
Date: Wed, 16 Sep 2026 12:21:16 -0400
Message-ID: <20260916162116.211261-1-sashal@kernel.org>
In-Reply-To: <2026091606-limpness-compost-f319@gregkh>
References: <2026091606-limpness-compost-f319@gregkh>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

From: Zihan Xi <zihanx@nebusec.ai>

[ Upstream commit b7ee18725f2292ab554aa96a101ae42d45f008bd ]

A netadmin in a user+net namespace can create many IPv4 and IPv6
multicast routing tables with MRT_TABLE and MRT6_TABLE. Each unseen
id allocates an mr_table via the shared mr_table_alloc(), links it
into the per-net list, 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.

Unresolved MFC entries are still allocated from softIRQ with
GFP_ATOMIC and are not charged. They expire after 10 seconds and are
bounded by the socket receive queue; see commit 0079ad8e8dc3
("ipmr: remove hard code cache_resolve_queue_len limit").

Fixes: f0ad0860d01e ("ipv4: ipmr: support multiple tables")
Fixes: d1db275dd3f6 ("ipv6: ip6mr: support multiple tables")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Signed-off-by: Zihan Xi <zihanx@nebusec.ai>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/050b58f7fc6b45da0fb12768ebb62d18fa46133d.1788784801.git.zihanx@nebusec.ai
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ adapted upstream allocation helpers to existing kzalloc() and kmem_cache_create() calls. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 6e4f91e76e2d3..f17b36a978486 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -3130,7 +3130,8 @@ int __init ip_mr_init(void)
 
 	mrt_cachep = kmem_cache_create("ip_mrt_cache",
 				       sizeof(struct mfc_cache),
-				       0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
+				       0, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
+				       SLAB_ACCOUNT,
 				       NULL);
 
 	err = register_pernet_subsys(&ipmr_net_ops);
diff --git a/net/ipv4/ipmr_base.c b/net/ipv4/ipmr_base.c
index 8b5b6f196cdc4..fb9796e21074f 100644
--- a/net/ipv4/ipmr_base.c
+++ b/net/ipv4/ipmr_base.c
@@ -38,7 +38,7 @@ mr_table_alloc(struct net *net, u32 id,
 	struct mr_table *mrt;
 	int err;
 
-	mrt = kzalloc(sizeof(*mrt), GFP_KERNEL);
+	mrt = kzalloc(sizeof(*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 c6fc951b01476..43bb75ea93898 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1357,7 +1357,7 @@ int __init ip6_mr_init(void)
 
 	mrt_cachep = kmem_cache_create("ip6_mrt_cache",
 				       sizeof(struct mfc6_cache),
-				       0, SLAB_HWCACHE_ALIGN,
+				       0, SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT,
 				       NULL);
 	if (!mrt_cachep)
 		return -ENOMEM;
-- 
2.53.0