Subject: FAILED: patch "[PATCH] ipmr: account multicast table and route memory" failed to apply to 5.15-stable tree
To: zihanx@nebusec.ai,idosch@nvidia.com,kuba@kernel.org,vega@nebusec.ai
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Wed, 16 Sep 2026 09:11:06 +0100
Message-ID: <2026091606-neurosis-primp-db10@gregkh>
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The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x b7ee18725f2292ab554aa96a101ae42d45f008bd
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026091606-neurosis-primp-db10@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:


thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b7ee18725f2292ab554aa96a101ae42d45f008bd Mon Sep 17 00:00:00 2001
From: Zihan Xi <zihanx@nebusec.ai>
Date: Tue, 8 Sep 2026 11:58:39 +0000
Subject: [PATCH] ipmr: account multicast table and route memory

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>

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;