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Adjust SP-GiST WAL record formats to reduce alignment padding.

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The way the code was written, the padding was copied from uninitialized
memory areas.. Because the structs are local variables in the code where
the WAL records are constructed, making them larger and zeroing the padding
bytes would not make the code very pretty, so rather than fixing this
directly by zeroing out the padding bytes, it seems more clear to not try to
align the tuples in the WAL records. The redo functions are taught to copy
the tuple header to a local variable to avoid unaligned access.

Stable-branches have the same problem, but we can't change the WAL format
there, so fix in master only. Reading a few random extra bytes at the stack
is harmless in practice, so it's not worth crafting a different
back-patchable fix.

Per reports from Kevin Grittner and Andres Freund, using clang static
analyzer and Valgrind, respectively.
This commit is contained in:
Heikki Linnakangas
2014-06-05 12:55:35 +03:00
parent d4d48a5edd
commit 8776faa81c
5 changed files with 105 additions and 80 deletions
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26
src/backend/access/spgist/spgdoinsert.c
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@ -217,7 +217,6 @@ addLeafTuple(Relation index, SpGistState *state, SpGistLeafTuple leafTuple,
xlrec.nodeI = 0;
ACCEPT_RDATA_DATA(&xlrec, sizeof(xlrec), 0);
/* we assume sizeof(xlrec) is at least int-aligned */
ACCEPT_RDATA_DATA(leafTuple, leafTuple->size, 1);
ACCEPT_RDATA_BUFFER(current->buffer, 2);
@ -533,9 +532,9 @@ moveLeafs(Relation index, SpGistState *state,
{
XLogRecPtr recptr;
ACCEPT_RDATA_DATA(&xlrec, MAXALIGN(sizeof(xlrec)), 0);
ACCEPT_RDATA_DATA(toDelete, MAXALIGN(sizeof(OffsetNumber) * nDelete), 1);
ACCEPT_RDATA_DATA(toInsert, MAXALIGN(sizeof(OffsetNumber) * nInsert), 2);
ACCEPT_RDATA_DATA(&xlrec, SizeOfSpgxlogMoveLeafs, 0);
ACCEPT_RDATA_DATA(toDelete, sizeof(OffsetNumber) * nDelete, 1);
ACCEPT_RDATA_DATA(toInsert, sizeof(OffsetNumber) * nInsert, 2);
ACCEPT_RDATA_DATA(leafdata, leafptr - leafdata, 3);
ACCEPT_RDATA_BUFFER(current->buffer, 4);
ACCEPT_RDATA_BUFFER(nbuf, 5);
@ -1116,9 +1115,8 @@ doPickSplit(Relation index, SpGistState *state,
leafdata = leafptr = (char *) palloc(totalLeafSizes);
ACCEPT_RDATA_DATA(&xlrec, MAXALIGN(sizeof(xlrec)), 0);
ACCEPT_RDATA_DATA(innerTuple, innerTuple->size, 1);
nRdata = 2;
ACCEPT_RDATA_DATA(&xlrec, SizeOfSpgxlogPickSplit, 0);
nRdata = 1;
/* Here we begin making the changes to the target pages */
START_CRIT_SECTION();
@ -1152,7 +1150,7 @@ doPickSplit(Relation index, SpGistState *state,
{
xlrec.nDelete = nToDelete;
ACCEPT_RDATA_DATA(toDelete,
MAXALIGN(sizeof(OffsetNumber) * nToDelete),
sizeof(OffsetNumber) * nToDelete,
nRdata);
nRdata++;
ACCEPT_RDATA_BUFFER(current->buffer, nRdata);
@ -1251,13 +1249,11 @@ doPickSplit(Relation index, SpGistState *state,
}
xlrec.nInsert = nToInsert;
ACCEPT_RDATA_DATA(toInsert,
MAXALIGN(sizeof(OffsetNumber) * nToInsert),
nRdata);
ACCEPT_RDATA_DATA(toInsert, sizeof(OffsetNumber) * nToInsert, nRdata);
nRdata++;
ACCEPT_RDATA_DATA(leafPageSelect,
MAXALIGN(sizeof(uint8) * nToInsert),
nRdata);
ACCEPT_RDATA_DATA(leafPageSelect, sizeof(uint8) * nToInsert, nRdata);
nRdata++;
ACCEPT_RDATA_DATA(innerTuple, innerTuple->size, nRdata);
nRdata++;
ACCEPT_RDATA_DATA(leafdata, leafptr - leafdata, nRdata);
nRdata++;
@ -1518,7 +1514,6 @@ spgAddNodeAction(Relation index, SpGistState *state,
xlrec.newPage = false;
ACCEPT_RDATA_DATA(&xlrec, sizeof(xlrec), 0);
/* we assume sizeof(xlrec) is at least int-aligned */
ACCEPT_RDATA_DATA(newInnerTuple, newInnerTuple->size, 1);
ACCEPT_RDATA_BUFFER(current->buffer, 2);
@ -1733,7 +1728,6 @@ spgSplitNodeAction(Relation index, SpGistState *state,
xlrec.newPage = false;
ACCEPT_RDATA_DATA(&xlrec, sizeof(xlrec), 0);
/* we assume sizeof(xlrec) is at least int-aligned */
ACCEPT_RDATA_DATA(prefixTuple, prefixTuple->size, 1);
ACCEPT_RDATA_DATA(postfixTuple, postfixTuple->size, 2);
ACCEPT_RDATA_BUFFER(current->buffer, 3);