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

[Daniel-Constantin Mierla]

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
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