From: Florian Westphal <fw@xxxxxxxxx>
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: 20a69341f2d0 ("netfilter: nf_tables: add netlink set API")
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/netfilter/nf_tables_api.c | 114 ++++------------------------------
1 file changed, 13 insertions(+), 101 deletions(-)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index eff496a6891b..1a132b800c8c 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2829,6 +2829,15 @@ 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;
@@ -2847,6 +2856,9 @@ 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;
@@ -7811,106 +7823,6 @@ 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
*
@@ -8046,7 +7958,7 @@ 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;
}
--
2.30.2
