`pdgbtrf` potential buffer overrun

[TLCFEM]

The DLAMOV call in the following implies the size of A be DBPTR + ( LLDA - 1 ) * BN, if the trailing LLDA - 1 - BM elements are not accessed, this number is DBPTR + ( LLDA - 1 ) * BN - ( LLDA - 1 - BM ).

scalapack/SRC/pdgbtrf.f

Lines 817 to 837 in a23c2cd

	IF( MYCOL.NE.NPCOL-1 ) THEN
	BM = BW - LBWU
	BN = BW
	ELSE
	BM = MIN( BW, ODD_SIZE ) + BWU
	BN = MIN( BW, ODD_SIZE )
	END IF
	*
	* Pointer to first element of block bidiagonal matrix in AF
	* Leading dimension of block bidiagonal system
	*
	BBPTR = ( NB+BWU )*BW + 1
	LDBB = 2*BW + BWU
	*
	* Copy from A and AF into block bidiagonal matrix (tail of AF)
	*
	* DBPTR = Pointer to diagonal blocks in A
	DBPTR = BW + 1 + LBWU + LN*LLDA
	*
	CALL DLAMOV( 'G', BM, BN, A( DBPTR ), LLDA-1, AF( BBPTR+BW*LDBB ),
	$ LDBB )

From the assignment, assuming 1x1 grid, then LBWU = BWU, LN = N - BW, BN = BW, BM = BW + BWU.

scalapack/SRC/pdgbtrf.f

Lines 699 to 718 in a23c2cd

	IF( MYCOL.NE.0 ) THEN
	LBWL = BW
	LBWU = 0
	APTR = 1
	ELSE
	LBWL = BWL
	LBWU = BWU
	APTR = 1 + BWU
	END IF
	*
	IF( MYCOL.NE.NPCOL-1 ) THEN
	LM = NB - LBWU
	LN = NB - BW
	ELSE IF( MYCOL.NE.0 ) THEN
	LM = ODD_SIZE + BWU
	LN = MAX( ODD_SIZE-BW, 0 )
	ELSE
	LM = N
	LN = MAX( N-BW, 0 )
	END IF

The number is

  BW + 1 + BWU + ( N - BW ) * LLDA + ( LLDA - 1 ) * BN - ( LLDA - 1 - BM ) - 1
= BW + 1 + BWU + N * LLDA - BW * LLDA + ( LLDA - 1 ) * BW - ( LLDA - 1 - BW - BWU ) - 1
= BW + 1 + BWU + N * LLDA - BW * LLDA + LLDA * BW -  BW - LLDA + 1 + BW + BWU - 1
= BW + 1 + 2 * BWU - LLDA + N * LLDA

So apart from the block N * LLDA, there is an additional part BW + 1 + 2 * BWU - LLDA.
If LLDA = 2 * BW +1, and BW = BWU + BWL, then

BW + 1 + 2 * BWU - LLDA = BW + 1 + 2 * BWU - 2 * BW - 1 = 2 * BWU - BW = BWU - BWL

If BWU is different from BWL, A needs to be extended to avoid buffer overrun.