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Commit 1947e4c3 authored by Florian Westphal's avatar Florian Westphal Committed by Greg Kroah-Hartman
Browse files

netfilter: nf_tables: prefer nft_chain_validate 



commit cff3bd012a9512ac5ed858d38e6ed65f6391008c upstream

nft_chain_validate already performs loop detection because a cycle will
result in a call stack overflow (ctx->level >= NFT_JUMP_STACK_SIZE).

It also follows maps via ->validate callback in nft_lookup, so there
appears no reason to iterate the maps again.

nf_tables_check_loops() and all its helper functions can be removed.
This improves ruleset load time significantly, from 23s down to 12s.

This also fixes a crash bug. Old loop detection code can result in
unbounded recursion:

BUG: TASK stack guard page was hit at ....
Oops: stack guard page: 0000 [#1] PREEMPT SMP KASAN
CPU: 4 PID: 1539 Comm: nft Not tainted 6.10.0-rc5+ #1
[..]

with a suitable ruleset during validation of register stores.

I can't see any actual reason to attempt to check for this from
nft_validate_register_store(), at this point the transaction is still in
progress, so we don't have a full picture of the rule graph.

For nf-next it might make sense to either remove it or make this depend
on table->validate_state in case we could catch an error earlier
(for improved error reporting to userspace).

Fixes: 20a69341 ("netfilter: nf_tables: add netlink set API")
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f8dfda79

net/netfilter/nf_tables_api.c

+13 −101
Original line number Diff line number Diff line
@@ -2698,6 +2698,15 @@ static void nf_tables_rule_release(const struct nft_ctx *ctx, 
	nf_tables_rule_destroy(ctx, rule);

}



/** nft_chain_validate - loop detection and hook validation

 *

 * @ctx: context containing call depth and base chain

 * @chain: chain to validate

 *

 * Walk through the rules of the given chain and chase all jumps/gotos

 * and set lookups until either the jump limit is hit or all reachable

 * chains have been validated.

 */

int nft_chain_validate(const struct nft_ctx *ctx, const struct nft_chain *chain)

{

	struct nft_expr *expr, *last;
@@ -2716,6 +2725,9 @@ int nft_chain_validate(const struct nft_ctx *ctx, const struct nft_chain *chain) 
			if (!expr->ops->validate)

				continue;



			/* This may call nft_chain_validate() recursively,

			 * callers that do so must increment ctx->level.

			 */

			err = expr->ops->validate(ctx, expr, &data);

			if (err < 0)

				return err;
@@ -7418,106 +7430,6 @@ int nft_chain_validate_hooks(const struct nft_chain *chain, 
}

EXPORT_SYMBOL_GPL(nft_chain_validate_hooks);



/*

 * Loop detection - walk through the ruleset beginning at the destination chain

 * of a new jump until either the source chain is reached (loop) or all

 * reachable chains have been traversed.

 *

 * The loop check is performed whenever a new jump verdict is added to an

 * expression or verdict map or a verdict map is bound to a new chain.

 */



static int nf_tables_check_loops(const struct nft_ctx *ctx,

				 const struct nft_chain *chain);



static int nf_tables_loop_check_setelem(const struct nft_ctx *ctx,

					struct nft_set *set,

					const struct nft_set_iter *iter,

					struct nft_set_elem *elem)

{

	const struct nft_set_ext *ext = nft_set_elem_ext(set, elem->priv);

	const struct nft_data *data;



	if (nft_set_ext_exists(ext, NFT_SET_EXT_FLAGS) &&

	    *nft_set_ext_flags(ext) & NFT_SET_ELEM_INTERVAL_END)

		return 0;



	data = nft_set_ext_data(ext);

	switch (data->verdict.code) {

	case NFT_JUMP:

	case NFT_GOTO:

		return nf_tables_check_loops(ctx, data->verdict.chain);

	default:

		return 0;

	}

}



static int nf_tables_check_loops(const struct nft_ctx *ctx,

				 const struct nft_chain *chain)

{

	const struct nft_rule *rule;

	const struct nft_expr *expr, *last;

	struct nft_set *set;

	struct nft_set_binding *binding;

	struct nft_set_iter iter;



	if (ctx->chain == chain)

		return -ELOOP;



	list_for_each_entry(rule, &chain->rules, list) {

		nft_rule_for_each_expr(expr, last, rule) {

			struct nft_immediate_expr *priv;

			const struct nft_data *data;

			int err;



			if (strcmp(expr->ops->type->name, "immediate"))

				continue;



			priv = nft_expr_priv(expr);

			if (priv->dreg != NFT_REG_VERDICT)

				continue;



			data = &priv->data;

			switch (data->verdict.code) {

			case NFT_JUMP:

			case NFT_GOTO:

				err = nf_tables_check_loops(ctx,

							data->verdict.chain);

				if (err < 0)

					return err;

			default:

				break;

			}

		}

	}



	list_for_each_entry(set, &ctx->table->sets, list) {

		if (!nft_is_active_next(ctx->net, set))

			continue;

		if (!(set->flags & NFT_SET_MAP) ||

		    set->dtype != NFT_DATA_VERDICT)

			continue;



		list_for_each_entry(binding, &set->bindings, list) {

			if (!(binding->flags & NFT_SET_MAP) ||

			    binding->chain != chain)

				continue;



			iter.genmask	= nft_genmask_next(ctx->net);

			iter.skip 	= 0;

			iter.count	= 0;

			iter.err	= 0;

			iter.fn		= nf_tables_loop_check_setelem;



			set->ops->walk(ctx, set, &iter);

			if (iter.err < 0)

				return iter.err;

		}

	}



	return 0;

}



/**

 *	nft_parse_u32_check - fetch u32 attribute and check for maximum value

 *
@@ -7653,7 +7565,7 @@ static int nft_validate_register_store(const struct nft_ctx *ctx, 
		if (data != NULL &&

		    (data->verdict.code == NFT_GOTO ||

		     data->verdict.code == NFT_JUMP)) {

			err = nf_tables_check_loops(ctx, data->verdict.chain);

			err = nft_chain_validate(ctx, data->verdict.chain);

			if (err < 0)

				return err;

		}