[sr-dev] git:master:74c84c7c: db_postgres: Fix heap use after free error in db_postgres module

Daniel-Constantin Mierla miconda at gmail.com
Fri Sep 4 12:21:02 CEST 2015


One more thing:

some code related to a report on bug tracker was removed:

-	memset(keywords, 0, (sizeof(char*) * 10));
-	memset(values, 0, (sizeof(char*) * 10));
-	memset(to, 0, (sizeof(char) * 16));


Was this intentional and related to your case? It is not related to
columns from pg result.

Cheers,
Daniel

On 04/09/15 12:07, Daniel-Constantin Mierla wrote:
> Hello,
>
> following the discussion started by Chris Double, I am not sure this is
> the right fix. The column names are now allocated in pkg, but don't get
> freed, so looks like this commit introduced a memory leak. See:
>
> http://lists.sip-router.org/pipermail/sr-dev/2015-September/030565.html
>
> I think the commit has to be reverted and then remove
> db_postgres_free_query() at the end of db_postgres_store_result()
>
> Not using postgres module, but this seems the right from c coding point
> of view comparing with db_mysql.
>
> Cheers,
> Daniel
>
> On 28/08/15 12:11, Carsten Bock wrote:
>> Module: kamailio
>> Branch: master
>> Commit: 74c84c7cd52347fcd1c90e75dca239b5f758169b
>> URL: https://github.com/kamailio/kamailio/commit/74c84c7cd52347fcd1c90e75dca239b5f758169b
>>
>> Author: Carsten Bock <carsten at ng-voice.com>
>> Committer: Carsten Bock <carsten at ng-voice.com>
>> Date: 2015-08-28T12:11:25+02:00
>>
>> db_postgres: Fix heap use after free error in db_postgres module
>>
>> The result structure for a query holds a pointer returned by
>> PQfname. When sql_do_query executes the query it gets this
>> database result structure returned but the PQfname pointer
>> has already been free'd by a call to db_postgres_free_query
>> from within db_postgres_store_result.
>>
>> sql_do_query then tries to copy the free'd string into another
>> result structure resulting in a heap use after free.
>>
>> The fix here copies the PQfname result.
>>
>> Fix by Chris Double
>>
>> ---
>>
>> Modified: modules/db_postgres/km_pg_con.c
>> Modified: modules/db_postgres/km_res.c
>>
>> ---
>>
>> Diff:  https://github.com/kamailio/kamailio/commit/74c84c7cd52347fcd1c90e75dca239b5f758169b.diff
>> Patch: https://github.com/kamailio/kamailio/commit/74c84c7cd52347fcd1c90e75dca239b5f758169b.patch
>>
>> ---
>>
>> diff --git a/modules/db_postgres/km_pg_con.c b/modules/db_postgres/km_pg_con.c
>> index ec98add..d053c55 100644
>> --- a/modules/db_postgres/km_pg_con.c
>> +++ b/modules/db_postgres/km_pg_con.c
>> @@ -71,10 +71,6 @@ struct pg_con* db_postgres_new_connection(struct db_id* id)
>>  	memset(ptr, 0, sizeof(struct pg_con));
>>  	ptr->ref = 1;
>>  
>> -	memset(keywords, 0, (sizeof(char*) * 10));
>> -	memset(values, 0, (sizeof(char*) * 10));
>> -	memset(to, 0, (sizeof(char) * 16));
>> -
>>  	if (id->port) {
>>  		ports = int2str(id->port, 0);
>>  		keywords[i] = "port";
>> diff --git a/modules/db_postgres/km_res.c b/modules/db_postgres/km_res.c
>> index e9aa232..912206b 100644
>> --- a/modules/db_postgres/km_res.c
>> +++ b/modules/db_postgres/km_res.c
>> @@ -126,8 +126,14 @@ int db_postgres_get_columns(const db1_con_t* _h, db1_res_t* _r)
>>  				RES_NAMES(_r)[col]);
>>  
>>  		/* The pointer that is here returned is part of the result structure. */
>> -		RES_NAMES(_r)[col]->s = PQfname(CON_RESULT(_h), col);
>> -		RES_NAMES(_r)[col]->len = strlen(PQfname(CON_RESULT(_h), col));
>> +		RES_NAMES(_r)[col]->s = pkg_malloc(strlen(PQfname(CON_RESULT(_h), col))+1);
>> +		if (! RES_NAMES(_r)[col]->s) {
>> +			LM_ERR("no private memory left\n");
>> +			db_free_columns(_r);
>> +			return -4;
>> +		}
>> +		strcpy(RES_NAMES(_r)[col]->s, PQfname(CON_RESULT(_h), col));
>> +		RES_NAMES(_r)[col]->len = strlen(RES_NAMES(_r)[col]->s);
>>  
>>  		LM_DBG("RES_NAMES(%p)[%d]=[%.*s]\n", RES_NAMES(_r)[col], col,
>>  				RES_NAMES(_r)[col]->len, RES_NAMES(_r)[col]->s);
>>
>>
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-- 
Daniel-Constantin Mierla
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Book: SIP Routing With Kamailio - http://www.asipto.com




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