[m.korotkov@postgrespro.ru]

Hi all,
I found a case of potential NULL pointer dereference.
In src/backend/utils/hash/dynahash.c in function HTAB *hash_create() the 
result of the DynaHashAlloc() is used unsafely.
The function DynaHashAlloc() calls MemoryContextAllocExtended() with 
MCXT_ALLOC_NO_OOM and can return a NULL pointer.
Added the pointer check for avoiding a potential problem.
---
Best regards, Korotkov Maksim
PostgresPro
m.korotkov@postgrespro.ru

Attachments:

0001-dynahash-add-memory-allocation-failure-check.patch (text/x-diff, 1.2K) download
From 75916a6855bb9e96c7b34b76c0380edc157c150c Mon Sep 17 00:00:00 2001
From: Maksim Korotkov <m.korotkov@postgrespro.ru>
Date: Tue, 22 Apr 2025 12:20:58 +0300
Subject: [PATCH] dynahash: add memory allocation failure check
 The function DynaHashAlloc() calls MemoryContextAllocExtended() with MCXT_ALLOC_NO_OOM
 and can return a NULL pointer.
 Fixes: e3860ffa4dd ("Initial pgindent run with pg_bsd_indent version 2.0.")
 Signed-off-by: Maksim Korotkov <m.korotkov@postgrespro.ru>

---
 src/backend/utils/hash/dynahash.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/backend/utils/hash/dynahash.c b/src/backend/utils/hash/dynahash.c
index 3f25929f2d8..0cfee50dc21 100644
--- a/src/backend/utils/hash/dynahash.c
+++ b/src/backend/utils/hash/dynahash.c
@@ -391,6 +391,12 @@ hash_create(const char *tabname, long nelem, const HASHCTL *info, int flags)
 
 	/* Initialize the hash header, plus a copy of the table name */
 	hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) + 1);
+	if (unlikely(hashp == NULL))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory")));
+	}
 	MemSet(hashp, 0, sizeof(HTAB));
 
 	hashp->tabname = (char *) (hashp + 1);
-- 
2.34.1