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Fix uninitialized memory propagation mistakes

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Valgrind complains that some uninitialized bytes are being passed around
by the extended statistics code since commit 7b504eb282ca2f, as reported
by Andres Freund.  Silence it.

Tomas Vondra submitted a patch which he verified to fix the complaints
in his machine; however I messed with it a bit before pushing, so any
remaining problems are likely my (Álvaro's) fault.

Author: Tomas Vondra
Discussion: https://postgr.es/m/20170325211031.4xxoptigqxm2emn2@alap3.anarazel.de
This commit is contained in:
Alvaro Herrera 2017-03-27 14:52:19 -03:00
parent 6e31c3e135
commit 6462238f0d
2 changed files with 60 additions and 34 deletions
src
backend/statistics
mvdistinct.c
include/statistics
statistics.h

87
src/backend/statistics/mvdistinct.c

@ -161,10 +161,10 @@ statext_ndistinct_serialize(MVNDistinct *ndistinct)
Assert(ndistinct->type == STATS_NDISTINCT_TYPE_BASIC);
/*
* Base size is base struct size, plus one base struct for each items,
* including number of items for each.
* Base size is size of scalar fields in the struct, plus one base struct
* for each item, including number of items for each.
*/
len = VARHDRSZ + offsetof(MVNDistinct, items) +
len = VARHDRSZ + SizeOfMVNDistinct +
ndistinct->nitems * (offsetof(MVNDistinctItem, attrs) + sizeof(int));
/* and also include space for the actual attribute numbers */
@ -182,9 +182,13 @@ statext_ndistinct_serialize(MVNDistinct *ndistinct)
tmp = VARDATA(output);
/* Store the base struct values */
memcpy(tmp, ndistinct, offsetof(MVNDistinct, items));
tmp += offsetof(MVNDistinct, items);
/* Store the base struct values (magic, type, nitems) */
memcpy(tmp, &ndistinct->magic, sizeof(uint32));
tmp += sizeof(uint32);
memcpy(tmp, &ndistinct->type, sizeof(uint32));
tmp += sizeof(uint32);
memcpy(tmp, &ndistinct->nitems, sizeof(uint32));
tmp += sizeof(uint32);
/*
* store number of attributes and attribute numbers for each ndistinct
@ -224,49 +228,64 @@ MVNDistinct *
statext_ndistinct_deserialize(bytea *data)
{
int i;
Size expected_size;
Size minimum_size;
MVNDistinct ndist;
MVNDistinct *ndistinct;
char *tmp;
if (data == NULL)
return NULL;
if (VARSIZE_ANY_EXHDR(data) < offsetof(MVNDistinct, items))
/* we expect at least the basic fields of MVNDistinct struct */
if (VARSIZE_ANY_EXHDR(data) < SizeOfMVNDistinct)
elog(ERROR, "invalid MVNDistinct size %ld (expected at least %ld)",
VARSIZE_ANY_EXHDR(data), offsetof(MVNDistinct, items));
/* read the MVNDistinct header */
ndistinct = (MVNDistinct *) palloc(sizeof(MVNDistinct));
VARSIZE_ANY_EXHDR(data), SizeOfMVNDistinct);
/* initialize pointer to the data part (skip the varlena header) */
tmp = VARDATA_ANY(data);
/* get the header and perform basic sanity checks */
memcpy(ndistinct, tmp, offsetof(MVNDistinct, items));
tmp += offsetof(MVNDistinct, items);
/* read the header fields and perform basic sanity checks */
memcpy(&ndist.magic, tmp, sizeof(uint32));
tmp += sizeof(uint32);
memcpy(&ndist.type, tmp, sizeof(uint32));
tmp += sizeof(uint32);
memcpy(&ndist.nitems, tmp, sizeof(uint32));
tmp += sizeof(uint32);
if (ndistinct->magic != STATS_NDISTINCT_MAGIC)
elog(ERROR, "invalid ndistinct magic %d (expected %d)",
ndistinct->magic, STATS_NDISTINCT_MAGIC);
if (ndistinct->type != STATS_NDISTINCT_TYPE_BASIC)
elog(ERROR, "invalid ndistinct type %d (expected %d)",
ndistinct->type, STATS_NDISTINCT_TYPE_BASIC);
Assert(ndistinct->nitems > 0);
if (ndist.magic != STATS_NDISTINCT_MAGIC)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("invalid ndistinct magic %08x (expected %08x)",
ndist.magic, STATS_NDISTINCT_MAGIC)));
if (ndist.type != STATS_NDISTINCT_TYPE_BASIC)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("invalid ndistinct type %d (expected %d)",
ndist.type, STATS_NDISTINCT_TYPE_BASIC)));
if (ndist.nitems == 0)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("invalid zero-length item array in MVNDistinct")));
/* what minimum bytea size do we expect for those parameters */
expected_size = offsetof(MVNDistinct, items) +
ndistinct->nitems * (offsetof(MVNDistinctItem, attrs) +
sizeof(AttrNumber) * 2);
minimum_size = (SizeOfMVNDistinct +
ndist.nitems * (SizeOfMVNDistinctItem +
sizeof(AttrNumber) * 2));
if (VARSIZE_ANY_EXHDR(data) < minimum_size)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("invalid MVNDistinct size %ld (expected at least %ld)",
VARSIZE_ANY_EXHDR(data), minimum_size)));
if (VARSIZE_ANY_EXHDR(data) < expected_size)
elog(ERROR, "invalid dependencies size %ld (expected at least %ld)",
VARSIZE_ANY_EXHDR(data), expected_size);
/* allocate space for the ndistinct items */
ndistinct = repalloc(ndistinct, offsetof(MVNDistinct, items) +
(ndistinct->nitems * sizeof(MVNDistinctItem)));
/*
* Allocate space for the ndistinct items (no space for each item's attnos:
* those live in bitmapsets allocated separately)
*/
ndistinct = palloc0(MAXALIGN(SizeOfMVNDistinct) +
(ndist.nitems * sizeof(MVNDistinctItem)));
ndistinct->magic = ndist.magic;
ndistinct->type = ndist.type;
ndistinct->nitems = ndist.nitems;
for (i = 0; i < ndistinct->nitems; i++)
{

7
src/include/statistics/statistics.h

@ -27,6 +27,9 @@ typedef struct MVNDistinctItem
double ndistinct; /* ndistinct value for this combination */
Bitmapset *attrs; /* attr numbers of items */
} MVNDistinctItem;
/* size of the struct, excluding attribute list */
#define SizeOfMVNDistinctItem \
(offsetof(MVNDistinctItem, ndistinct) + sizeof(double))
/* A MVNDistinct object, comprising all possible combinations of columns */
typedef struct MVNDistinct
@ -37,6 +40,10 @@ typedef struct MVNDistinct
MVNDistinctItem items[FLEXIBLE_ARRAY_MEMBER];
} MVNDistinct;
/* size of the struct excluding the items array */
#define SizeOfMVNDistinct (offsetof(MVNDistinct, nitems) + sizeof(uint32))
extern MVNDistinct *statext_ndistinct_load(Oid mvoid);
extern void BuildRelationExtStatistics(Relation onerel, double totalrows,