Fix use of dangling pointer in heap_delete() when logging replica identity

When logging the replica identity of a deleted tuple, XLOG_HEAP_DELETE
records include references of the old tuple.  Its data is stored in an
intermediate variable used to register this information for the WAL
record, but this variable gets away from the stack when the record gets
actually inserted.

Spotted by clang's AddressSanitizer.

Author: Stas Kelvish
Discussion: https://postgr.es/m/085C8825-AD86-4E93-AF80-E26CDF03D1EA@postgrespro.ru
Backpatch-through: 9.4

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index c7dd2be6fc1fdf5878ea755e778d3ba99ef18fa5..0a9aafb7b62888164af959da837746ed34853c6c 100644 (file)
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -3290,6 +3290,7 @@ l1:
    if (RelationNeedsWAL(relation))
    {
        xl_heap_delete xlrec;
+       xl_heap_header xlhdr;
        XLogRecPtr  recptr;
 
        /* For logical decode we need combocids to properly decode the catalog */
@@ -3320,8 +3321,6 @@ l1:
         */
        if (old_key_tuple != NULL)
        {
-           xl_heap_header xlhdr;
-
            xlhdr.t_infomask2 = old_key_tuple->t_data->t_infomask2;
            xlhdr.t_infomask = old_key_tuple->t_data->t_infomask;
            xlhdr.t_hoff = old_key_tuple->t_data->t_hoff;