BUG #14927: Unchecked SearchSysCache1() return value

The following bug has been logged on the website:

Bug reference: 14927
Logged by: Pan Bian
Email address: bianpan2016(at)163(dot)com
PostgreSQL version: 10.1
Operating system: Linux
Description:

File: postgresql-10.1/src/backend/catalog/heap.c
Function: heap_drop_with_catalog
Line: 1771

Function SearchSysCache1() may return a NULL pointer, but in
heap_drop_with_catalog(), its return value is not validated before it is
dereferenced. To avoid NULL dereference, it is better to check the return
value of SearchSysCache1() against NULL.

For your convenience, I paste related codes as follows:

1771 tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
1772 if (((Form_pg_class) GETSTRUCT(tuple))->relispartition)
1773 {
1774 parentOid = get_partition_parent(relid);
1775 LockRelationOid(parentOid, AccessExclusiveLock);
1776 }
1777
1778 ReleaseSysCache(tuple);

Thank you!

Pan Bian