From 79f2b5d583e2e2a7ccd13e31d0e20a900c8f2f61 Mon Sep 17 00:00:00 2001 From: Tom Lane <tgl@sss.pgh.pa.us> Date: Mon, 25 May 2015 21:56:19 -0400 Subject: [PATCH] Fix valgrind's "unaddressable bytes" whining about BRIN code. brin_form_tuple calculated an exact tuple size, then palloc'd and filled just that much. Later, brin_doinsert or brin_doupdate would MAXALIGN the tuple size and tell PageAddItem that that was the size of the tuple to insert. If the original tuple size wasn't a multiple of MAXALIGN, the net result would be that PageAddItem would memcpy a few more bytes than the palloc request had been for. AFAICS, this is totally harmless in the real world: the error is a read overrun not a write overrun, and palloc would certainly have rounded the request up to a MAXALIGN multiple internally, so there's no chance of the memcpy fetching off the end of memory. Valgrind, however, is picky to the byte level not the MAXALIGN level. Fix it by pushing the MAXALIGN step back to brin_form_tuple. (The other possible source of tuples in this code, brin_form_placeholder_tuple, was already producing a MAXALIGN'd result.) In passing, be a bit more paranoid about internal allocations in brin_form_tuple. --- src/backend/access/brin/brin_pageops.c | 4 ++-- src/backend/access/brin/brin_tuple.c | 15 +++++++++++---- 2 files changed, 13 insertions(+), 6 deletions(-) diff --git a/src/backend/access/brin/brin_pageops.c b/src/backend/access/brin/brin_pageops.c index ce4cbadf21a..0b257d913b6 100644 --- a/src/backend/access/brin/brin_pageops.c +++ b/src/backend/access/brin/brin_pageops.c @@ -55,7 +55,7 @@ brin_doupdate(Relation idxrel, BlockNumber pagesPerRange, Buffer newbuf; bool extended = false; - newsz = MAXALIGN(newsz); + Assert(newsz == MAXALIGN(newsz)); /* make sure the revmap is long enough to contain the entry we need */ brinRevmapExtend(revmap, heapBlk); @@ -273,7 +273,7 @@ brin_doinsert(Relation idxrel, BlockNumber pagesPerRange, ItemPointerData tid; bool extended = false; - itemsz = MAXALIGN(itemsz); + Assert(itemsz == MAXALIGN(itemsz)); /* Make sure the revmap is long enough to contain the entry we need */ brinRevmapExtend(revmap, heapBlk); diff --git a/src/backend/access/brin/brin_tuple.c b/src/backend/access/brin/brin_tuple.c index 72356c066c7..5a7462b59cf 100644 --- a/src/backend/access/brin/brin_tuple.c +++ b/src/backend/access/brin/brin_tuple.c @@ -103,9 +103,10 @@ brin_form_tuple(BrinDesc *brdesc, BlockNumber blkno, BrinMemTuple *tuple, Assert(brdesc->bd_totalstored > 0); - values = palloc(sizeof(Datum) * brdesc->bd_totalstored); - nulls = palloc0(sizeof(bool) * brdesc->bd_totalstored); - phony_nullbitmap = palloc(sizeof(bits8) * BITMAPLEN(brdesc->bd_totalstored)); + values = (Datum *) palloc(sizeof(Datum) * brdesc->bd_totalstored); + nulls = (bool *) palloc0(sizeof(bool) * brdesc->bd_totalstored); + phony_nullbitmap = (bits8 *) + palloc(sizeof(bits8) * BITMAPLEN(brdesc->bd_totalstored)); /* * Set up the values/nulls arrays for heap_fill_tuple @@ -144,6 +145,9 @@ brin_form_tuple(BrinDesc *brdesc, BlockNumber blkno, BrinMemTuple *tuple, values[idxattno++] = tuple->bt_columns[keyno].bv_values[datumno]; } + /* Assert we did not overrun temp arrays */ + Assert(idxattno <= brdesc->bd_totalstored); + /* compute total space needed */ len = SizeOfBrinTuple; if (anynulls) @@ -160,12 +164,15 @@ brin_form_tuple(BrinDesc *brdesc, BlockNumber blkno, BrinMemTuple *tuple, data_len = heap_compute_data_size(brtuple_disk_tupdesc(brdesc), values, nulls); - len += data_len; + len = MAXALIGN(len); + rettuple = palloc0(len); rettuple->bt_blkno = blkno; rettuple->bt_info = hoff; + + /* Assert that hoff fits in the space available */ Assert((rettuple->bt_info & BRIN_OFFSET_MASK) == hoff); /* -- GitLab