v2-detect-double-free-with-requested_size.patch

diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index 161c2e2d3df..bea9e47ee4f 100644
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -1175,6 +1175,10 @@ AllocSetFree(void *pointer)
 		link = GetFreeListLink(chunk);
 
 #ifdef MEMORY_CONTEXT_CHECKING
+		/* Test for previously-freed chunk */
+		if (unlikely(chunk->requested_size == InvalidAllocSize))
+			elog(WARNING, "detected double pfree in %s %p",
+				 set->header.name, chunk);
 		/* Test for someone scribbling on unused space in chunk */
 		if (chunk->requested_size < GetChunkSizeFromFreeListIdx(fidx))
 			if (!sentinel_ok(pointer, chunk->requested_size))
@@ -1373,6 +1377,10 @@ AllocSetRealloc(void *pointer, Size size, int flags)
 	oldchksize = GetChunkSizeFromFreeListIdx(fidx);
 
 #ifdef MEMORY_CONTEXT_CHECKING
+	/* Test for previously-freed chunk */
+	if (unlikely(chunk->requested_size == InvalidAllocSize))
+		elog(WARNING, "detected realloc of freed chunk in %s %p",
+			 set->header.name, chunk);
 	/* Test for someone scribbling on unused space in chunk */
 	if (chunk->requested_size < oldchksize)
 		if (!sentinel_ok(pointer, chunk->requested_size))
diff --git a/src/backend/utils/mmgr/generation.c b/src/backend/utils/mmgr/generation.c
index 9077ed299b4..fe9d087c85e 100644
--- a/src/backend/utils/mmgr/generation.c
+++ b/src/backend/utils/mmgr/generation.c
@@ -762,6 +762,10 @@ GenerationFree(void *pointer)
 	}
 
 #ifdef MEMORY_CONTEXT_CHECKING
+	/* Test for previously-freed chunk */
+	if (unlikely(chunk->requested_size == InvalidAllocSize))
+		elog(WARNING, "detected double pfree in %s %p",
+			 ((MemoryContext) block->context)->name, chunk);
 	/* Test for someone scribbling on unused space in chunk */
 	Assert(chunk->requested_size < chunksize);
 	if (!sentinel_ok(pointer, chunk->requested_size))
@@ -867,6 +871,10 @@ GenerationRealloc(void *pointer, Size size, int flags)
 	set = block->context;
 
 #ifdef MEMORY_CONTEXT_CHECKING
+	/* Test for previously-freed chunk */
+	if (unlikely(chunk->requested_size == InvalidAllocSize))
+		elog(WARNING, "detected realloc of freed chunk in %s %p",
+			 ((MemoryContext) set)->name, chunk);
 	/* Test for someone scribbling on unused space in chunk */
 	Assert(chunk->requested_size < oldsize);
 	if (!sentinel_ok(pointer, chunk->requested_size))
diff --git a/src/backend/utils/mmgr/slab.c b/src/backend/utils/mmgr/slab.c
index bd00bab18fe..0d1e6285c29 100644
--- a/src/backend/utils/mmgr/slab.c
+++ b/src/backend/utils/mmgr/slab.c
@@ -539,6 +539,7 @@ SlabAllocSetupNewChunk(MemoryContext context, SlabBlock *block,
 	MemoryChunkSetHdrMask(chunk, block, MAXALIGN(slab->chunkSize), MCTX_SLAB_ID);
 
 #ifdef MEMORY_CONTEXT_CHECKING
+	chunk->requested_size = size;
 	/* slab mark to catch clobber of "unused" space */
 	Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
 	set_sentinel(MemoryChunkGetPointer(chunk), size);
@@ -748,11 +749,17 @@ SlabFree(void *pointer)
 	slab = block->slab;
 
 #ifdef MEMORY_CONTEXT_CHECKING
+	/* Test for previously-freed chunk */
+	if (unlikely(chunk->requested_size == InvalidAllocSize))
+		elog(WARNING, "detected double pfree in %s %p",
+			 slab->header.name, chunk);
 	/* Test for someone scribbling on unused space in chunk */
 	Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
 	if (!sentinel_ok(pointer, slab->chunkSize))
 		elog(WARNING, "detected write past chunk end in %s %p",
 			 slab->header.name, chunk);
+	/* Reset requested_size to InvalidAllocSize in free chunks */
+	chunk->requested_size = InvalidAllocSize;
 #endif
 
 	/* push this chunk onto the head of the block's free list */