Commit ee666a54 authored Nov 04, 2024 by Florian Westphal Committed by Pablo Neira Ayuso Nov 05, 2024

netfilter: nf_tables: must hold rcu read lock while iterating expression type list



nft shell tests trigger:
 WARNING: suspicious RCU usage
 net/netfilter/nf_tables_api.c:3125 RCU-list traversed in non-reader section!!
 1 lock held by nft/2068:
  #0: ffff888106c6f8c8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nf_tables_valid_genid+0x3c/0xf0

But the transaction mutex doesn't protect this list, the nfnl subsystem
mutex would, but we can't acquire it here without risk of ABBA
deadlocks.

Acquire the rcu read lock to avoid this issue.

v3: add a comment that explains the ->inner_ops check implies
expression is builtin and lack of a module owner reference is ok.

Fixes: 3a07327d ("netfilter: nft_inner: support for inner tunnel header matching")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent 3567146b

net/netfilter/nf_tables_api.c

+18 −6

Original line number	Diff line number	Diff line
		@@ -3296,25 +3296,37 @@ int nft_expr_inner_parse(const struct nft_ctx ctx, const struct nlattr nla,
		if (!tb[NFTA_EXPR_DATA] \|\| !tb[NFTA_EXPR_NAME])
		return -EINVAL;

		rcu_read_lock();

		type = __nft_expr_type_get(ctx->family, tb[NFTA_EXPR_NAME]);
		if (!type)
		return -ENOENT;
		if (!type) {
		err = -ENOENT;
		goto out_unlock;
		}

		if (!type->inner_ops)
		return -EOPNOTSUPP;
		if (!type->inner_ops) {
		err = -EOPNOTSUPP;
		goto out_unlock;
		}

		err = nla_parse_nested_deprecated(info->tb, type->maxattr,
		tb[NFTA_EXPR_DATA],
		type->policy, NULL);
		if (err < 0)
		goto err_nla_parse;
		goto out_unlock;

		info->attr = nla;
		info->ops = type->inner_ops;

		/* No module reference will be taken on type->owner.
		* Presence of type->inner_ops implies that the expression
		* is builtin, so it cannot go away.
		*/
		rcu_read_unlock();
		return 0;

		err_nla_parse:
		out_unlock:
		rcu_read_unlock();
		return err;
		}