[Patch] Fix bounds check in trim_array()
Hi,
while working on something else i encountered a bug in the trim_array()
function. The bounds check fails for empty arrays without any
dimensions. It reads the size of the non existing first dimension to
determine the arrays length.
select trim_array('{}'::int[], 10);
------------
{}
select trim_array('{}'::int[], 100);
ERROR: number of elements to trim must be between 0 and 64
The attached patch fixes that check.
Martin
Attachments:
0001-Fix-bounds-check-in-trim_array.patchtext/x-patch; charset=UTF-8; name=0001-Fix-bounds-check-in-trim_array.patchDownload+4-2
On Mon, Jul 25, 2022 at 04:40:51PM +0200, Martin Kalcher wrote:
+SELECT trim_array(ARRAY[]::int[], 1); -- fail +ERROR: number of elements to trim must be between 0 and 0
Can we improve the error message? Maybe it should look something like
ERROR: number of elements to trim must be 0
for this case.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
Nathan Bossart <nathandbossart@gmail.com> writes:
On Mon, Jul 25, 2022 at 04:40:51PM +0200, Martin Kalcher wrote:
+SELECT trim_array(ARRAY[]::int[], 1); -- fail +ERROR: number of elements to trim must be between 0 and 0
Can we improve the error message? Maybe it should look something like
ERROR: number of elements to trim must be 0
for this case.
Hmm, I'm unexcited about making our long-suffering translators
deal with another translatable string for such a corner case.
I think it's fine as-is.
A bigger problem is that a little further down, there's an equally
unprotected reference to ARR_LBOUND(v)[0]. Now, the fact that that
expression computes garbage doesn't matter too much, because AFAICS
if the array is zero-D then array_get_slice is going to exit at
if (ndim < nSubscripts || ndim <= 0 || ndim > MAXDIM)
return PointerGetDatum(construct_empty_array(elemtype));
without ever examining its upperIndx[] argument. However,
once we put in a test case covering this behavior, I bet that
valgrind-using buildfarm animals will start to bleat about the
invalid memory access. I think the easiest fix is like
if (ARR_NDIM(v) > 0)
{
upper[0] = ARR_LBOUND(v)[0] + array_length - n - 1;
upperProvided[0] = true;
}
It'd be good to get this fix into next week's minor releases,
so I'll go push it.
regards, tom lane