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Clean up assorted failures under clang's -fsanitize=undefined checks.
Most of these are cases where we could call memcpy() or other libc functions with a NULL pointer and a zero count, which is forbidden by POSIX even though every production version of libc allows it. We've fixed such things before in a piecemeal way, but apparently never made an effort to try to get them all. I don't claim that this patch does so either, but it gets every failure I observe in check-world, using clang 12.0.1 on current RHEL8. numeric.c has a different issue that the sanitizer doesn't like: "ln(-1.0)" will compute log10(0) and then try to assign the resulting -Inf to an integer variable. We don't actually use the result in such a case, so there's no live bug. Back-patch to all supported branches, with the idea that we might start running a buildfarm member that tests this case. This includes back-patching c1132aa (Check the size in COPY_POINTER_FIELD), which previously silenced some of these issues in copyfuncs.c. Discussion: https://postgr.es/m/CALNJ-vT9r0DSsAOw9OXVJFxLENoVS_68kJ5x0p44atoYH+H4dg@mail.gmail.com
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9 files changed

+31
-15
lines changed

9 files changed

+31
-15
lines changed

‎contrib/pgcrypto/px.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -198,7 +198,7 @@ combo_init(PX_Combo *cx, const uint8 *key, unsigned klen,
198198
ivbuf = palloc0(ivs);
199199
if (ivlen > ivs)
200200
memcpy(ivbuf, iv, ivs);
201-
else
201+
else if (ivlen > 0)
202202
memcpy(ivbuf, iv, ivlen);
203203
}
204204

‎src/backend/access/heap/heapam.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -328,7 +328,7 @@ initscan(HeapScanDesc scan, ScanKey key, bool keep_startblock)
328328
/*
329329
* copy the scan key, if appropriate
330330
*/
331-
if (key != NULL)
331+
if (key != NULL && scan->rs_base.rs_nkeys > 0)
332332
memcpy(scan->rs_base.rs_key, key, scan->rs_base.rs_nkeys * sizeof(ScanKeyData));
333333

334334
/*

‎src/backend/access/heap/heapam_visibility.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1564,8 +1564,8 @@ HeapTupleHeaderIsOnlyLocked(HeapTupleHeader tuple)
15641564
static bool
15651565
TransactionIdInArray(TransactionId xid, TransactionId *xip, Size num)
15661566
{
1567-
return bsearch(&xid, xip, num,
1568-
sizeof(TransactionId), xidComparator) != NULL;
1567+
return num > 0 &&
1568+
bsearch(&xid, xip, num, sizeof(TransactionId), xidComparator) != NULL;
15691569
}
15701570

15711571
/*

‎src/backend/access/transam/clog.c

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -297,8 +297,9 @@ TransactionIdSetPageStatus(TransactionId xid, int nsubxids,
297297
if (all_xact_same_page && xid == MyProc->xid &&
298298
nsubxids <= THRESHOLD_SUBTRANS_CLOG_OPT &&
299299
nsubxids == MyProc->subxidStatus.count &&
300-
memcmp(subxids, MyProc->subxids.xids,
301-
nsubxids * sizeof(TransactionId)) == 0)
300+
(nsubxids == 0 ||
301+
memcmp(subxids, MyProc->subxids.xids,
302+
nsubxids * sizeof(TransactionId)) == 0))
302303
{
303304
/*
304305
* If we can immediately acquire XactSLRULock, we update the status of

‎src/backend/access/transam/xact.c

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -5353,8 +5353,9 @@ SerializeTransactionState(Size maxsize, char *start_address)
53535353
{
53545354
if (FullTransactionIdIsValid(s->fullTransactionId))
53555355
workspace[i++] = XidFromFullTransactionId(s->fullTransactionId);
5356-
memcpy(&workspace[i], s->childXids,
5357-
s->nChildXids * sizeof(TransactionId));
5356+
if (s->nChildXids > 0)
5357+
memcpy(&workspace[i], s->childXids,
5358+
s->nChildXids * sizeof(TransactionId));
53585359
i += s->nChildXids;
53595360
}
53605361
Assert(i == nxids);

‎src/backend/storage/ipc/shm_mq.c

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -773,8 +773,11 @@ shm_mq_receive(shm_mq_handle *mqh, Size *nbytesp, void **datap, bool nowait)
773773

774774
/* Copy as much as we can. */
775775
Assert(mqh->mqh_partial_bytes + rb <= nbytes);
776-
memcpy(&mqh->mqh_buffer[mqh->mqh_partial_bytes], rawdata, rb);
777-
mqh->mqh_partial_bytes += rb;
776+
if (rb > 0)
777+
{
778+
memcpy(&mqh->mqh_buffer[mqh->mqh_partial_bytes], rawdata, rb);
779+
mqh->mqh_partial_bytes += rb;
780+
}
778781

779782
/*
780783
* Update count of bytes that can be consumed, accounting for

‎src/backend/utils/adt/numeric.c

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -10048,12 +10048,20 @@ exp_var(const NumericVar *arg, NumericVar *result, int rscale)
1004810048
*
1004910049
* Essentially, we're approximating log10(abs(ln(var))). This is used to
1005010050
* determine the appropriate rscale when computing natural logarithms.
10051+
*
10052+
* Note: many callers call this before range-checking the input. Therefore,
10053+
* we must be robust against values that are invalid to apply ln() to.
10054+
* We don't wish to throw an error here, so just return zero in such cases.
1005110055
*/
1005210056
static int
1005310057
estimate_ln_dweight(const NumericVar *var)
1005410058
{
1005510059
int ln_dweight;
1005610060

10061+
/* Caller should fail on ln(negative), but for the moment return zero */
10062+
if (var->sign != NUMERIC_POS)
10063+
return 0;
10064+
1005710065
if (cmp_var(var, &const_zero_point_nine) >= 0 &&
1005810066
cmp_var(var, &const_one_point_one) <= 0)
1005910067
{

‎src/backend/utils/time/snapmgr.c

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -536,12 +536,14 @@ SetTransactionSnapshot(Snapshot sourcesnap, VirtualTransactionId *sourcevxid,
536536
CurrentSnapshot->xmax = sourcesnap->xmax;
537537
CurrentSnapshot->xcnt = sourcesnap->xcnt;
538538
Assert(sourcesnap->xcnt <= GetMaxSnapshotXidCount());
539-
memcpy(CurrentSnapshot->xip, sourcesnap->xip,
540-
sourcesnap->xcnt * sizeof(TransactionId));
539+
if (sourcesnap->xcnt > 0)
540+
memcpy(CurrentSnapshot->xip, sourcesnap->xip,
541+
sourcesnap->xcnt * sizeof(TransactionId));
541542
CurrentSnapshot->subxcnt = sourcesnap->subxcnt;
542543
Assert(sourcesnap->subxcnt <= GetMaxSnapshotSubxidCount());
543-
memcpy(CurrentSnapshot->subxip, sourcesnap->subxip,
544-
sourcesnap->subxcnt * sizeof(TransactionId));
544+
if (sourcesnap->subxcnt > 0)
545+
memcpy(CurrentSnapshot->subxip, sourcesnap->subxip,
546+
sourcesnap->subxcnt * sizeof(TransactionId));
545547
CurrentSnapshot->suboverflowed = sourcesnap->suboverflowed;
546548
CurrentSnapshot->takenDuringRecovery = sourcesnap->takenDuringRecovery;
547549
/* NB: curcid should NOT be copied, it's a local matter */

‎src/fe_utils/print.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -966,7 +966,8 @@ print_aligned_text(const printTableContent *cont, FILE *fout, bool is_pager)
966966

967967
more_col_wrapping = col_count;
968968
curr_nl_line = 0;
969-
memset(header_done, false, col_count * sizeof(bool));
969+
if (col_count > 0)
970+
memset(header_done, false, col_count * sizeof(bool));
970971
while (more_col_wrapping)
971972
{
972973
if (opt_border == 2)

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