Segment crash (SIGSEGV) when creating in-place tablespace with empty LOCATION

[yjhjstz]

Bug Description

When creating an in-place tablespace with allow_in_place_tablespaces=on and empty LOCATION '', segment processes crash with SIGSEGV.

How to Reproduce

SET allow_in_place_tablespaces=on;
CREATE TABLESPACE dropme_ts1 LOCATION '';

The QD dispatches the CREATE TABLESPACE statement to QE segments. On the segments, stmt->location is NULL (not empty string), causing pstrdup(NULL) to crash.

Stack Trace from Segment Core Dump

#0  raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  StandardHandlerForSigillSigsegvSigbus_OnMainThread (processName="Segment process", postgres_signal_arg=11) at elog.c:5353
#2  CdbProgramErrorHandler (postgres_signal_arg=11) at postgres.c:3897
...
#5  __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:65
#6  MemoryContextStrdup (context=0x55f89dad74d0, string=0x0) at mcxt.c:1527
#7  pstrdup (in=0x0) at mcxt.c:1539
#8  CreateTableSpace (stmt=0x55f89dab2cc0) at tablespace.c:331

(gdb) p stmt->location
$1 = 0x0

Root Cause

In CreateTableSpace() (src/backend/commands/tablespace.c), line 331:

if (!location)
    location = pstrdup(stmt->location);

When CREATE TABLESPACE ... LOCATION '' is dispatched from QD to QE, the serialization/deserialization of CreateTableSpaceStmt converts the empty string "" to NULL. On the QE, pstrdup(NULL) causes a segfault.

Fix

Add a NULL guard:

if (!location)
    location = pstrdup(stmt->location ? stmt->location : "");

This preserves the in-place tablespace semantics (empty string = in-place) while preventing the NULL pointer dereference on segments.