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Commit6462238

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Fix uninitialized memory propagation mistakes
Valgrind complains that some uninitialized bytes are being passed aroundby the extended statistics code since commit7b504eb, as reportedby Andres Freund. Silence it.Tomas Vondra submitted a patch which he verified to fix the complaintsin his machine; however I messed with it a bit before pushing, so anyremaining problems are likely my (Álvaro's) fault.Author: Tomas VondraDiscussion:https://postgr.es/m/20170325211031.4xxoptigqxm2emn2@alap3.anarazel.de
1 parent6e31c3e commit6462238

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2 files changed

+61
-35
lines changed

2 files changed

+61
-35
lines changed

‎src/backend/statistics/mvdistinct.c‎

Lines changed: 54 additions & 35 deletions
Original file line numberDiff line numberDiff line change
@@ -161,10 +161,10 @@ statext_ndistinct_serialize(MVNDistinct *ndistinct)
161161
Assert(ndistinct->type==STATS_NDISTINCT_TYPE_BASIC);
162162

163163
/*
164-
* Base size isbase struct size, plus one base struct for each items,
165-
* including number of items for each.
164+
* Base size issize of scalar fields in the struct, plus one base struct
165+
*for each item,including number of items for each.
166166
*/
167-
len=VARHDRSZ+offsetof(MVNDistinct,items)+
167+
len=VARHDRSZ+SizeOfMVNDistinct+
168168
ndistinct->nitems* (offsetof(MVNDistinctItem,attrs)+sizeof(int));
169169

170170
/* and also include space for the actual attribute numbers */
@@ -182,9 +182,13 @@ statext_ndistinct_serialize(MVNDistinct *ndistinct)
182182

183183
tmp=VARDATA(output);
184184

185-
/* Store the base struct values */
186-
memcpy(tmp,ndistinct, offsetof(MVNDistinct,items));
187-
tmp+= offsetof(MVNDistinct,items);
185+
/* Store the base struct values (magic, type, nitems) */
186+
memcpy(tmp,&ndistinct->magic,sizeof(uint32));
187+
tmp+=sizeof(uint32);
188+
memcpy(tmp,&ndistinct->type,sizeof(uint32));
189+
tmp+=sizeof(uint32);
190+
memcpy(tmp,&ndistinct->nitems,sizeof(uint32));
191+
tmp+=sizeof(uint32);
188192

189193
/*
190194
* store number of attributes and attribute numbers for each ndistinct
@@ -224,49 +228,64 @@ MVNDistinct *
224228
statext_ndistinct_deserialize(bytea*data)
225229
{
226230
inti;
227-
Sizeexpected_size;
231+
Sizeminimum_size;
232+
MVNDistinctndist;
228233
MVNDistinct*ndistinct;
229234
char*tmp;
230235

231236
if (data==NULL)
232237
returnNULL;
233238

234-
if (VARSIZE_ANY_EXHDR(data)< offsetof(MVNDistinct,items))
239+
/* we expect at least the basic fields of MVNDistinct struct */
240+
if (VARSIZE_ANY_EXHDR(data)<SizeOfMVNDistinct)
235241
elog(ERROR,"invalid MVNDistinct size %ld (expected at least %ld)",
236-
VARSIZE_ANY_EXHDR(data), offsetof(MVNDistinct,items));
237-
238-
/* read the MVNDistinct header */
239-
ndistinct= (MVNDistinct*)palloc(sizeof(MVNDistinct));
242+
VARSIZE_ANY_EXHDR(data),SizeOfMVNDistinct);
240243

241244
/* initialize pointer to the data part (skip the varlena header) */
242245
tmp=VARDATA_ANY(data);
243246

244-
/* get the header and perform basic sanity checks */
245-
memcpy(ndistinct,tmp, offsetof(MVNDistinct,items));
246-
tmp+= offsetof(MVNDistinct,items);
247-
248-
if (ndistinct->magic!=STATS_NDISTINCT_MAGIC)
249-
elog(ERROR,"invalid ndistinct magic %d (expected %d)",
250-
ndistinct->magic,STATS_NDISTINCT_MAGIC);
251-
252-
if (ndistinct->type!=STATS_NDISTINCT_TYPE_BASIC)
253-
elog(ERROR,"invalid ndistinct type %d (expected %d)",
254-
ndistinct->type,STATS_NDISTINCT_TYPE_BASIC);
255-
256-
Assert(ndistinct->nitems>0);
247+
/* read the header fields and perform basic sanity checks */
248+
memcpy(&ndist.magic,tmp,sizeof(uint32));
249+
tmp+=sizeof(uint32);
250+
memcpy(&ndist.type,tmp,sizeof(uint32));
251+
tmp+=sizeof(uint32);
252+
memcpy(&ndist.nitems,tmp,sizeof(uint32));
253+
tmp+=sizeof(uint32);
254+
255+
if (ndist.magic!=STATS_NDISTINCT_MAGIC)
256+
ereport(ERROR,
257+
(errcode(ERRCODE_DATA_CORRUPTED),
258+
errmsg("invalid ndistinct magic %08x (expected %08x)",
259+
ndist.magic,STATS_NDISTINCT_MAGIC)));
260+
if (ndist.type!=STATS_NDISTINCT_TYPE_BASIC)
261+
ereport(ERROR,
262+
(errcode(ERRCODE_DATA_CORRUPTED),
263+
errmsg("invalid ndistinct type %d (expected %d)",
264+
ndist.type,STATS_NDISTINCT_TYPE_BASIC)));
265+
if (ndist.nitems==0)
266+
ereport(ERROR,
267+
(errcode(ERRCODE_DATA_CORRUPTED),
268+
errmsg("invalid zero-length item array in MVNDistinct")));
257269

258270
/* what minimum bytea size do we expect for those parameters */
259-
expected_size= offsetof(MVNDistinct,items)+
260-
ndistinct->nitems* (offsetof(MVNDistinctItem,attrs)+
261-
sizeof(AttrNumber)*2);
271+
minimum_size= (SizeOfMVNDistinct+
272+
ndist.nitems* (SizeOfMVNDistinctItem+
273+
sizeof(AttrNumber)*2));
274+
if (VARSIZE_ANY_EXHDR(data)<minimum_size)
275+
ereport(ERROR,
276+
(errcode(ERRCODE_DATA_CORRUPTED),
277+
errmsg("invalid MVNDistinct size %ld (expected at least %ld)",
278+
VARSIZE_ANY_EXHDR(data),minimum_size)));
262279

263-
if (VARSIZE_ANY_EXHDR(data)<expected_size)
264-
elog(ERROR,"invalid dependencies size %ld (expected at least %ld)",
265-
VARSIZE_ANY_EXHDR(data),expected_size);
266-
267-
/* allocate space for the ndistinct items */
268-
ndistinct=repalloc(ndistinct, offsetof(MVNDistinct,items)+
269-
(ndistinct->nitems*sizeof(MVNDistinctItem)));
280+
/*
281+
* Allocate space for the ndistinct items (no space for each item's attnos:
282+
* those live in bitmapsets allocated separately)
283+
*/
284+
ndistinct=palloc0(MAXALIGN(SizeOfMVNDistinct)+
285+
(ndist.nitems*sizeof(MVNDistinctItem)));
286+
ndistinct->magic=ndist.magic;
287+
ndistinct->type=ndist.type;
288+
ndistinct->nitems=ndist.nitems;
270289

271290
for (i=0;i<ndistinct->nitems;i++)
272291
{

‎src/include/statistics/statistics.h‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,9 @@ typedef struct MVNDistinctItem
2727
doublendistinct;/* ndistinct value for this combination */
2828
Bitmapset*attrs;/* attr numbers of items */
2929
}MVNDistinctItem;
30+
/* size of the struct, excluding attribute list */
31+
#defineSizeOfMVNDistinctItem \
32+
(offsetof(MVNDistinctItem, ndistinct) + sizeof(double))
3033

3134
/* A MVNDistinct object, comprising all possible combinations of columns */
3235
typedefstructMVNDistinct
@@ -37,6 +40,10 @@ typedef struct MVNDistinct
3740
MVNDistinctItemitems[FLEXIBLE_ARRAY_MEMBER];
3841
}MVNDistinct;
3942

43+
/* size of the struct excluding the items array */
44+
#defineSizeOfMVNDistinct(offsetof(MVNDistinct, nitems) + sizeof(uint32))
45+
46+
4047
externMVNDistinct*statext_ndistinct_load(Oidmvoid);
4148

4249
externvoidBuildRelationExtStatistics(Relationonerel,doubletotalrows,

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