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netfilter: flowtable: publish GC-visible tuple last

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nf_flow_table_iterate() only treats original-direction tuple nodes as
owning entries. Publishing the original node first lets GC observe and
free a flow while flow_offload_add() is still inserting the reply node.
Publish the reply node first and the original node last so GC never
sees a partially installed flow.

KASAN can trigger slab-use-after-free read and write reports in the
flowtable/rhashtable path (rht_deferred_worker, jhash, flow_offload_del,
flow_offload_lookup, etc.).

Fixes: ac2a66665e ("netfilter: add generic flow table infrastructure")
Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
Assisted-by: Codex:gpt-5
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Jérémy Jean
2026-08-08 12:40:02 +00:00
committed by Pablo Neira Ayuso
parent d02f592064
commit 2014ac62df
1 changed files with 4 additions and 3 deletions
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7
net/netfilter/nf_flow_table_core.c
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@@ -332,17 +332,18 @@ int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload *flow)
flow->timeout = nf_flowtable_time_stamp + flow_offload_get_timeout(flow);
err = rhashtable_insert_fast(&flow_table->rhashtable,
&flow->tuplehash[0].node,
&flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].node,
nf_flow_offload_rhash_params);
if (err < 0)
return err;
/* GC only iterates original-direction entries; publish original last. */
err = rhashtable_insert_fast(&flow_table->rhashtable,
&flow->tuplehash[1].node,
&flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].node,
nf_flow_offload_rhash_params);
if (err < 0) {
rhashtable_remove_fast(&flow_table->rhashtable,
&flow->tuplehash[0].node,
&flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].node,
nf_flow_offload_rhash_params);
return err;
}