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Re: [PATCH] netfilter: ip_tables: remove useless variable assignment in get_info()

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Hi Joe,

Quoting Joe Perches <joe@perches.com>:

> On Mon, 2017-06-26 at 17:34 -0500, Gustavo A. R. Silva wrote:
>> Value assigned to variable _ret_ at line 970 is overwritten either at
>> line 986 or 988, before it can be used. This makes such variable
>> assignment useless.
>>
>> Addresses-Coverity-ID: 1226932
> []
>> diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
> []
>> @@ -967,7 +967,7 @@ static int get_info(struct net *net, void __user *user,
>>  		struct xt_table_info tmp;
>>
>>  		if (compat) {
>> -			ret = compat_table_info(private, &tmp);
>> +			compat_table_info(private, &tmp);
>
> why isn't it more appropriate to test the return value?
>

Oh, in this particular case, based on git blame, the code has been  
like that for more than 10 years. So my reasoning was that if it  
hasn't been fixed yet, maybe that return value is not relevant.

But in case it turns out to actually be relevant, what do you think  
about the following patch:

--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -968,7 +968,8 @@ static int get_info(struct net *net, void __user *user,

                 if (compat) {
                         ret = compat_table_info(private, &tmp);
-                       xt_compat_flush_offsets(AF_INET);
+                       if (!ret)
+                               goto out;
                         private = &tmp;
                 }
  #endif
@@ -986,14 +987,20 @@ static int get_info(struct net *net, void __user *user,
                         ret = -EFAULT;
                 else
                         ret = 0;
+       } else
+               ret = -ENOENT;

+out:
+       if (t) {
                 xt_table_unlock(t);
                 module_put(t->me);
-       } else
-               ret = -ENOENT;
+       }
+
  #ifdef CONFIG_COMPAT
-       if (compat)
+       if (compat) {
+               xt_compat_flush_offsets(AF_INET);
                 xt_compat_unlock(AF_INET);
+       }
  #endif
         return ret;
  }


Thank you!
--
Gustavo A. R. Silva

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[PATCH] netfilter: ip_tables: remove useless variable assignment in  get_info() "Gustavo A. R. Silva" <garsilva@embeddedor.com> - 2017-06-27 00:40 +0200
  Re: [PATCH] netfilter: ip_tables: remove useless variable  assignment in get_info() Joe Perches <joe@perches.com> - 2017-06-27 04:50 +0200
    Re: [PATCH] netfilter: ip_tables: remove useless variable  assignment in get_info() "Gustavo A. R. Silva" <garsilva@embeddedor.com> - 2017-06-27 05:50 +0200

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