linux-kernel - Re: [PATCH][next] netfilter: nf_tables: Fix dereference of null pointer flow

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Message-ID: <20210625095901.GH2040@kadam>
Date:   Fri, 25 Jun 2021 12:59:01 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] netfilter: nf_tables: Fix dereference of null
 pointer flow

Btw, why is there no clean up if nft_table_validate() fails?

net/netfilter/nf_tables_api.c
  3432                                  list_add_tail_rcu(&rule->list, &old_rule->list);
  3433                          else
  3434                                  list_add_rcu(&rule->list, &chain->rules);
  3435                  }
  3436          }
  3437          kvfree(expr_info);
  3438          chain->use++;
  3439  
  3440          if (flow)
  3441                  nft_trans_flow_rule(trans) = flow;
  3442  
  3443          if (nft_net->validate_state == NFT_VALIDATE_DO)
  3444                  return nft_table_validate(net, table);
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The cleanup for this would be quite involved unfortunately...  Not
necessarily something to attempt without being able to test the code.

  3445  
  3446          return 0;
  3447  
  3448  err_destroy_flow_rule:
  3449          nft_flow_rule_destroy(flow);
  3450  err_release_rule:
  3451          nf_tables_rule_release(&ctx, rule);
  3452  err_release_expr:
  3453          for (i = 0; i < n; i++) {
  3454                  if (expr_info[i].ops) {
  3455                          module_put(expr_info[i].ops->type->owner);
  3456                          if (expr_info[i].ops->type->release_ops)
  3457                                  expr_info[i].ops->type->release_ops(expr_info[i].ops);
  3458                  }
  3459          }
  3460          kvfree(expr_info);
  3461  
  3462          return err;
  3463  }

regards,
dan carpenter