Subject: Avoid resource leak (contrib/postgres_fdw/connection.c)

From: Ranier Vilela <[email-masked]>
Date: Mon, 16 Mar 2026 08:45:49 -0300

Hi.

Per Coverity.

CID 1645716: (#1 of 1): Resource leak (RESOURCE_LEAK)
8. leaked_storage: Variable str going out of scope leaks the storage
str.data points to.

The function *postgres_fdw_connection* leaks the contents of
var str.data
Once that function *cstring_to_text* palloc the contents
must be necessary to free the var str.data.

patch attached.

best regards,
Ranier Vilelas

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From: Matheus Alcantara <[email-masked]>
Date: Mon, 16 Mar 2026 11:16:30 -0300

> must be necessary to free the var str.data.

Hi,

Thanks for the patch, it looks correct to me. I've searched for this 
pattern `PG_RETURN_TEXT_P(cstring_to_text(.*.data` in other places and 
I've just found on postgres_fdw/connection.c

I've also search for other cases of `return cstring_to_text(...)` 
usages and I didn't found anything that seems suspicious.

Tests are also passing.

--
Matheus Alcantara
EDB: https://www.enterprisedb.com

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From: Ranier Vilela <[email-masked]>
Date: Mon, 16 Mar 2026 11:18:54 -0300

Hi.

> usages and I didn't found anything that seems suspicious.
Thanks for taking a look.

best regards,
Ranier Vilela

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From: Fujii Masao <[email-masked]>
Date: Tue, 17 Mar 2026 08:07:47 +0900

On Mon, Mar 16, 2026 at 8:46 PM Ranier Vilela <[email-masked]> wrote:
> 8. leaked_storage: Variable str going out of scope leaks the storage str.data points to.
>

It seems that postgres_fdw_connection() is expected to be called by
ForeignServerConnectionString() via OidFunctionCall3(),
and to allocate memory (including str.data) in the FDWConnectionContext
memory context created by ForeignServerConnectionString().

After calling postgres_fdw_connection(), ForeignServerConnectionString()
deletes FDWConnectionContext. So it seems to me that any memory
allocated in that context, including str.data, would not leak. No?

Regards,

-- 
Fujii Masao

---

From: "Matheus Alcantara" <[email-masked]>
Date: Wed, 18 Mar 2026 14:42:35 -0300

> allocated in that context, including str.data, would not leak. No?

Yeah, this sounds correct, but I'm wondering if the current pfree 
calls on postgres_fdw_connection() is needed?

My previous review was assuming that any allocated memory on 
postgres_fdw_connection() should be free at the end because of these 
calls, but ForeignServerConnectionString() already assume that this 
function leak memory:
	/*
	 * GetForeignServer, GetForeignDataWrapper, and the connection function
	 * itself all leak memory into CurrentMemoryContext. Switch to a temporary
	 * context for easy cleanup.
	 */
	tempContext = AllocSetContextCreate(CurrentMemoryContext,
										"FDWConnectionContext",
										ALLOCSET_SMALL_SIZES);