FIX:linalg:Guard against possible permute_l out of bound behavior

scipy/linalg/_decomp_lu_cython.pyx

@@ -24,12 +24,12 @@ cdef void lu_decompose(cnp.ndarray[lapack_t, ndim=2] a,
                        int[::1] perm,
                        bint permute_l) noexcept:
     """LU decomposition and copy operations using ?getrf routines
-    
+
     This function overwrites inputs. For interfacing LAPACK,
     it creates a memory buffer and copies into with F-order
     then swaps back to C order hence no need for dealing with
     Fortran arrays which are inconvenient.
-    
+
     After the LU factorization, to minimize the amount of data
     copied, for rectangle arrays, and depending on the size,
     the smaller portion is copied out to U and the rest becomes
@@ -117,7 +117,7 @@ cdef void lu_decompose(cnp.ndarray[lapack_t, ndim=2] a,
         for ind1 in range(mn):
             a[ind1, ind1] = 1
             a[ind1, ind1+1:mn] = 0
-            
+
     else:  # square or fat, "a" holds bigger U
 
         lu[0, 0] = 1
@@ -128,22 +128,31 @@ cdef void lu_decompose(cnp.ndarray[lapack_t, ndim=2] a,
         for ind2 in range(mn - 1):  # cols
             for ind1 in range(ind2+1, m):  # rows
                 a[ind1, ind2] = 0
-    
+
     if permute_l:
         # b still exists -> use it as temp array
         # we copy everything to b and pick back
         # rows from b as dictated by perm
-        memcpy(bb, 
-               (&a[0, 0] if m > n else &lu[0, 0]),
-               m*n*sizeof(lapack_t)
-              )
-        for ind1 in range(m):
-            if perm[ind1] == ind1:  # Row is not permuted
-                continue
-            else:
-                memcpy((&a[ind1, 0] if m > n else &lu[ind1, 0]),
-                       bb + (perm[ind1]*mn),  # stride rows
-                       mn*sizeof(lapack_t))  # copy 1 row of mem
+
+        if m > n:
+            memcpy(bb, &a[0, 0], m*mn*sizeof(lapack_t))
+            for ind1 in range(m):
+                if perm[ind1] == ind1:
+                    continue
+                else:
+                    memcpy(&a[ind1, 0],
+                           bb + (perm[ind1]*mn),  # row stride
+                           mn*sizeof(lapack_t))  # copy one row of memory
+
+        else:  # same but for lu array
+            memcpy(bb, &lu[0, 0], mn*n*sizeof(lapack_t))
+            for ind1 in range(mn):
+                if perm[ind1] == ind1:
+                    continue
+                else:
+                    memcpy(&lu[ind1, 0],
+                           bb + (perm[ind1]*mn),
+                           mn*sizeof(lapack_t))
 
 
 @cython.nonecheck(False)