[PATCH 4.14 20/26] netfilter: nf_tables: report use refcount overflow

From: Pablo Neira Ayuso pablo@netfilter.org

commit 1689f25924ada8fe14a4a82c38925d04994c7142 upstream.

Overflow use refcount checks are not complete.

Add helper function to deal with object reference counter tracking. Report -EMFILE in case UINT_MAX is reached.

nft_use_dec() splats in case that reference counter underflows, which should not ever happen.

Add nft_use_inc_restore() and nft_use_dec_restore() which are used to restore reference counter from error and abort paths.

Use u32 in nft_flowtable and nft_object since helper functions cannot work on bitfields.

Remove the few early incomplete checks now that the helper functions are in place and used to check for refcount overflow.

Fixes: 96518518cc41 ("netfilter: add nftables") Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/netfilter/nf_tables.h | 27 ++++++- net/netfilter/nf_tables_api.c | 143 +++++++++++++++++++++++--------------- net/netfilter/nft_objref.c | 8 +- 3 files changed, 119 insertions(+), 59 deletions(-)

--- a/include/net/netfilter/nf_tables.h +++ b/include/net/netfilter/nf_tables.h @@ -968,6 +968,29 @@ int __nft_release_basechain(struct nft_c

unsigned int nft_do_chain(struct nft_pktinfo *pkt, void *priv);

+static inline bool nft_use_inc(u32 *use) +{ + if (*use == UINT_MAX) + return false; + + (*use)++; + + return true; +} + +static inline void nft_use_dec(u32 *use) +{ + WARN_ON_ONCE((*use)-- == 0); +} + +/* For error and abort path: restore use counter to previous state. */ +static inline void nft_use_inc_restore(u32 *use) +{ + WARN_ON_ONCE(!nft_use_inc(use)); +} + +#define nft_use_dec_restore nft_use_dec + /** * struct nft_table - nf_tables table * @@ -1051,8 +1074,8 @@ struct nft_object { struct list_head list; char *name; struct nft_table *table; - u32 genmask:2, - use:30; + u32 genmask:2; + u32 use; /* runtime data below here */ const struct nft_object_ops *ops ____cacheline_aligned; unsigned char data[] --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -248,7 +248,7 @@ static int nft_delchain(struct nft_ctx * if (err < 0) return err;

- ctx->table->use--; + nft_use_dec(&ctx->table->use); nft_deactivate_next(ctx->net, ctx->chain);

return err; @@ -289,7 +289,7 @@ nf_tables_delrule_deactivate(struct nft_ /* You cannot delete the same rule twice */ if (nft_is_active_next(ctx->net, rule)) { nft_deactivate_next(ctx->net, rule); - ctx->chain->use--; + nft_use_dec(&ctx->chain->use); return 0; } return -ENOENT; @@ -378,7 +378,7 @@ static int nft_delset(const struct nft_c return err;

nft_deactivate_next(ctx->net, set); - ctx->table->use--; + nft_use_dec(&ctx->table->use);

return err; } @@ -410,7 +410,7 @@ static int nft_delobj(struct nft_ctx *ct return err;

nft_deactivate_next(ctx->net, obj); - ctx->table->use--; + nft_use_dec(&ctx->table->use);

return err; } @@ -1421,9 +1421,6 @@ static int nf_tables_addchain(struct nft unsigned int i; int err;

- if (table->use == UINT_MAX) - return -EOVERFLOW; - if (nla[NFTA_CHAIN_HOOK]) { struct nft_chain_hook hook; struct nf_hook_ops *ops; @@ -1491,16 +1488,22 @@ static int nf_tables_addchain(struct nft if (err < 0) goto err1;

+ if (!nft_use_inc(&table->use)) { + err = -EMFILE; + goto err_use; + } + ctx->chain = chain; err = nft_trans_chain_add(ctx, NFT_MSG_NEWCHAIN); if (err < 0) goto err2;

- table->use++; list_add_tail_rcu(&chain->list, &table->chains);

return 0; err2: + nft_use_dec_restore(&table->use); +err_use: nf_tables_unregister_hooks(net, table, chain, afi->nops); err1: nf_tables_chain_destroy(chain); @@ -2371,9 +2374,6 @@ static int nf_tables_newrule(struct net if (!create || nlh->nlmsg_flags & NLM_F_REPLACE) return -EINVAL; handle = nf_tables_alloc_handle(table); - - if (chain->use == UINT_MAX) - return -EOVERFLOW; }

if (nla[NFTA_RULE_POSITION]) { @@ -2441,23 +2441,28 @@ static int nf_tables_newrule(struct net expr = nft_expr_next(expr); }

+ if (!nft_use_inc(&chain->use)) { + err = -EMFILE; + goto err2; + } + if (nlh->nlmsg_flags & NLM_F_REPLACE) { trans = nft_trans_rule_add(&ctx, NFT_MSG_NEWRULE, rule); if (trans == NULL) { err = -ENOMEM; - goto err2; + goto err_destroy_flow_rule; } err = nft_delrule(&ctx, old_rule); if (err < 0) { nft_trans_destroy(trans); - goto err2; + goto err_destroy_flow_rule; }

list_add_tail_rcu(&rule->list, &old_rule->list); } else { if (nft_trans_rule_add(&ctx, NFT_MSG_NEWRULE, rule) == NULL) { err = -ENOMEM; - goto err2; + goto err_destroy_flow_rule; }

if (nlh->nlmsg_flags & NLM_F_APPEND) { @@ -2472,9 +2477,11 @@ static int nf_tables_newrule(struct net list_add_rcu(&rule->list, &chain->rules); } } - chain->use++; + return 0;

+err_destroy_flow_rule: + nft_use_dec_restore(&chain->use); err2: nft_rule_expr_deactivate(&ctx, rule, NFT_TRANS_PREPARE_ERROR); nf_tables_rule_destroy(&ctx, rule); @@ -3262,10 +3269,15 @@ static int nf_tables_newset(struct net * if (ops->privsize != NULL) size = ops->privsize(nla, &desc);

+ if (!nft_use_inc(&table->use)) { + err = -EMFILE; + goto err1; + } + set = kvzalloc(sizeof(*set) + size + udlen, GFP_KERNEL); if (!set) { err = -ENOMEM; - goto err1; + goto err_alloc; }

name = nla_strdup(nla[NFTA_SET_NAME], GFP_KERNEL); @@ -3310,7 +3322,7 @@ static int nf_tables_newset(struct net * goto err4;

list_add_tail_rcu(&set->list, &table->sets); - table->use++; + return 0;

err4: @@ -3319,6 +3331,8 @@ err3: kfree(set->name); err2: kvfree(set); +err_alloc: + nft_use_dec_restore(&table->use); err1: module_put(ops->type->owner); return err; @@ -3393,9 +3407,6 @@ int nf_tables_bind_set(const struct nft_ struct nft_set_binding *i; struct nft_set_iter iter;

- if (set->use == UINT_MAX) - return -EOVERFLOW; - if (!list_empty(&set->bindings) && set->flags & NFT_SET_ANONYMOUS) return -EBUSY;

@@ -3420,10 +3431,12 @@ int nf_tables_bind_set(const struct nft_ return iter.err; } bind: + if (!nft_use_inc(&set->use)) + return -EMFILE; + binding->chain = ctx->chain; list_add_tail_rcu(&binding->list, &set->bindings); nft_set_trans_bind(ctx, set); - set->use++;

return 0; } @@ -3448,7 +3461,7 @@ void nf_tables_activate_set(const struct if (set->flags & NFT_SET_ANONYMOUS) nft_clear(ctx->net, set);

- set->use++; + nft_use_inc_restore(&set->use); } EXPORT_SYMBOL_GPL(nf_tables_activate_set);

@@ -3464,17 +3477,17 @@ void nf_tables_deactivate_set(const stru else list_del_rcu(&binding->list);

- set->use--; + nft_use_dec(&set->use); break; case NFT_TRANS_PREPARE: if (set->flags & NFT_SET_ANONYMOUS) nft_deactivate_next(ctx->net, set);

- set->use--; + nft_use_dec(&set->use); return; case NFT_TRANS_ABORT: case NFT_TRANS_RELEASE: - set->use--; + nft_use_dec(&set->use); /* fall through */ default: nf_tables_unbind_set(ctx, set, binding, @@ -3947,7 +3960,7 @@ void nft_set_elem_destroy(const struct n if (destroy_expr && nft_set_ext_exists(ext, NFT_SET_EXT_EXPR)) nf_tables_expr_destroy(NULL, nft_set_ext_expr(ext)); if (nft_set_ext_exists(ext, NFT_SET_EXT_OBJREF)) - (*nft_set_ext_obj(ext))->use--; + nft_use_dec(&(*nft_set_ext_obj(ext))->use); kfree(elem); } EXPORT_SYMBOL_GPL(nft_set_elem_destroy); @@ -4090,8 +4103,16 @@ static int nft_add_set_elem(struct nft_c set->objtype, genmask); if (IS_ERR(obj)) { err = PTR_ERR(obj); + obj = NULL; goto err2; } + + if (!nft_use_inc(&obj->use)) { + err = -EMFILE; + obj = NULL; + goto err2; + } + nft_set_ext_add(&tmpl, NFT_SET_EXT_OBJREF); }

@@ -4150,10 +4171,8 @@ static int nft_add_set_elem(struct nft_c udata->len = ulen - 1; nla_memcpy(&udata->data, nla[NFTA_SET_ELEM_USERDATA], ulen); } - if (obj) { + if (obj) *nft_set_ext_obj(ext) = obj; - obj->use++; - }

trans = nft_trans_elem_alloc(ctx, NFT_MSG_NEWSETELEM, set); if (trans == NULL) @@ -4199,13 +4218,14 @@ err6: err5: kfree(trans); err4: - if (obj) - obj->use--; kfree(elem.priv); err3: if (nla[NFTA_SET_ELEM_DATA] != NULL) nft_data_release(&elem.data.val, desc.type); err2: + if (obj) + nft_use_dec_restore(&obj->use); + nft_data_release(&elem.key.val, NFT_DATA_VALUE); err1: return err; @@ -4266,11 +4286,14 @@ static int nf_tables_newsetelem(struct n */ void nft_data_hold(const struct nft_data *data, enum nft_data_types type) { + struct nft_chain *chain; + if (type == NFT_DATA_VERDICT) { switch (data->verdict.code) { case NFT_JUMP: case NFT_GOTO: - data->verdict.chain->use++; + chain = data->verdict.chain; + nft_use_inc_restore(&chain->use); break; } } @@ -4285,7 +4308,7 @@ static void nft_set_elem_activate(const if (nft_set_ext_exists(ext, NFT_SET_EXT_DATA)) nft_data_hold(nft_set_ext_data(ext), set->dtype); if (nft_set_ext_exists(ext, NFT_SET_EXT_OBJREF)) - (*nft_set_ext_obj(ext))->use++; + nft_use_inc_restore(&(*nft_set_ext_obj(ext))->use); }

static void nft_set_elem_deactivate(const struct net *net, @@ -4297,7 +4320,7 @@ static void nft_set_elem_deactivate(cons if (nft_set_ext_exists(ext, NFT_SET_EXT_DATA)) nft_data_release(nft_set_ext_data(ext), set->dtype); if (nft_set_ext_exists(ext, NFT_SET_EXT_OBJREF)) - (*nft_set_ext_obj(ext))->use--; + nft_use_dec(&(*nft_set_ext_obj(ext))->use); }

static int nft_del_setelem(struct nft_ctx *ctx, struct nft_set *set, @@ -4672,9 +4695,14 @@ static int nf_tables_newobj(struct net *

nft_ctx_init(&ctx, net, skb, nlh, afi, table, NULL, nla);

+ if (!nft_use_inc(&table->use)) + return -EMFILE; + type = nft_obj_type_get(objtype); - if (IS_ERR(type)) - return PTR_ERR(type); + if (IS_ERR(type)) { + err = PTR_ERR(type); + goto err_type; + }

obj = nft_obj_init(&ctx, type, nla[NFTA_OBJ_DATA]); if (IS_ERR(obj)) { @@ -4693,7 +4721,7 @@ static int nf_tables_newobj(struct net * goto err3;

list_add_tail_rcu(&obj->list, &table->objects); - table->use++; + return 0; err3: kfree(obj->name); @@ -4703,6 +4731,9 @@ err2: kfree(obj); err1: module_put(type->owner); +err_type: + nft_use_dec_restore(&table->use); + return err; }

@@ -5304,7 +5335,7 @@ static int nf_tables_commit(struct net * */ if (nft_trans_set(trans)->flags & NFT_SET_ANONYMOUS && !list_empty(&nft_trans_set(trans)->bindings)) - trans->ctx.table->use--; + nft_use_dec(&trans->ctx.table->use);

nf_tables_set_notify(&trans->ctx, nft_trans_set(trans), NFT_MSG_NEWSET, GFP_KERNEL); @@ -5418,7 +5449,7 @@ static int nf_tables_abort(struct net *n kfree(nft_trans_chain_name(trans)); nft_trans_destroy(trans); } else { - trans->ctx.table->use--; + nft_use_dec_restore(&trans->ctx.table->use); list_del_rcu(&trans->ctx.chain->list); nf_tables_unregister_hooks(trans->ctx.net, trans->ctx.table, @@ -5427,25 +5458,25 @@ static int nf_tables_abort(struct net *n } break; case NFT_MSG_DELCHAIN: - trans->ctx.table->use++; + nft_use_inc_restore(&trans->ctx.table->use); nft_clear(trans->ctx.net, trans->ctx.chain); nft_trans_destroy(trans); break; case NFT_MSG_NEWRULE: - trans->ctx.chain->use--; + nft_use_dec_restore(&trans->ctx.chain->use); list_del_rcu(&nft_trans_rule(trans)->list); nft_rule_expr_deactivate(&trans->ctx, nft_trans_rule(trans), NFT_TRANS_ABORT); break; case NFT_MSG_DELRULE: - trans->ctx.chain->use++; + nft_use_inc_restore(&trans->ctx.chain->use); nft_clear(trans->ctx.net, nft_trans_rule(trans)); nft_rule_expr_activate(&trans->ctx, nft_trans_rule(trans)); nft_trans_destroy(trans); break; case NFT_MSG_NEWSET: - trans->ctx.table->use--; + nft_use_dec_restore(&trans->ctx.table->use); if (nft_trans_set_bound(trans)) { nft_trans_destroy(trans); break; @@ -5453,7 +5484,7 @@ static int nf_tables_abort(struct net *n list_del_rcu(&nft_trans_set(trans)->list); break; case NFT_MSG_DELSET: - trans->ctx.table->use++; + nft_use_inc_restore(&trans->ctx.table->use); nft_clear(trans->ctx.net, nft_trans_set(trans)); nft_trans_destroy(trans); break; @@ -5477,11 +5508,11 @@ static int nf_tables_abort(struct net *n nft_trans_destroy(trans); break; case NFT_MSG_NEWOBJ: - trans->ctx.table->use--; + nft_use_dec_restore(&trans->ctx.table->use); list_del_rcu(&nft_trans_obj(trans)->list); break; case NFT_MSG_DELOBJ: - trans->ctx.table->use++; + nft_use_inc_restore(&trans->ctx.table->use); nft_clear(trans->ctx.net, nft_trans_obj(trans)); nft_trans_destroy(trans); break; @@ -5882,8 +5913,9 @@ static int nft_verdict_init(const struct return PTR_ERR(chain); if (nft_is_base_chain(chain)) return -EOPNOTSUPP; + if (!nft_use_inc(&chain->use)) + return -EMFILE;

- chain->use++; data->verdict.chain = chain; break; } @@ -5895,10 +5927,13 @@ static int nft_verdict_init(const struct

static void nft_verdict_uninit(const struct nft_data *data) { + struct nft_chain *chain; + switch (data->verdict.code) { case NFT_JUMP: case NFT_GOTO: - data->verdict.chain->use--; + chain = data->verdict.chain; + nft_use_dec(&chain->use); break; } } @@ -6059,11 +6094,11 @@ int __nft_release_basechain(struct nft_c ctx->afi->nops); list_for_each_entry_safe(rule, nr, &ctx->chain->rules, list) { list_del(&rule->list); - ctx->chain->use--; + nft_use_dec(&ctx->chain->use); nf_tables_rule_release(ctx, rule); } list_del(&ctx->chain->list); - ctx->table->use--; + nft_use_dec(&ctx->table->use); nf_tables_chain_destroy(ctx->chain);

return 0; @@ -6093,23 +6128,23 @@ static void __nft_release_afinfo(struct ctx.chain = chain; list_for_each_entry_safe(rule, nr, &chain->rules, list) { list_del(&rule->list); - chain->use--; + nft_use_dec(&chain->use); nf_tables_rule_release(&ctx, rule); } } list_for_each_entry_safe(set, ns, &table->sets, list) { list_del(&set->list); - table->use--; + nft_use_dec(&table->use); nft_set_destroy(set); } list_for_each_entry_safe(obj, ne, &table->objects, list) { list_del(&obj->list); - table->use--; + nft_use_dec(&table->use); nft_obj_destroy(obj); } list_for_each_entry_safe(chain, nc, &table->chains, list) { list_del(&chain->list); - table->use--; + nft_use_dec(&table->use); nf_tables_chain_destroy(chain); } list_del(&table->list); --- a/net/netfilter/nft_objref.c +++ b/net/netfilter/nft_objref.c @@ -43,8 +43,10 @@ static int nft_objref_init(const struct if (IS_ERR(obj)) return -ENOENT;

+ if (!nft_use_inc(&obj->use)) + return -EMFILE; + nft_objref_priv(expr) = obj; - obj->use++;

return 0; } @@ -73,7 +75,7 @@ static void nft_objref_deactivate(const if (phase == NFT_TRANS_COMMIT) return;

- obj->use--; + nft_use_dec(&obj->use); }

static void nft_objref_activate(const struct nft_ctx *ctx, @@ -81,7 +83,7 @@ static void nft_objref_activate(const st { struct nft_object *obj = nft_objref_priv(expr);

- obj->use++; + nft_use_inc_restore(&obj->use); }

static struct nft_expr_type nft_objref_type;