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Commitec5f71a

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Fix tuple_data_split() to not open a relation without any lock.
contrib/pageinspect's tuple_data_split() function thought it could getaway with opening the referenced relation with NoLock. In practicethere's no guarantee that the current session holds any lock on thatrel (even if we just read a page from it), so that this is unsafe.Switch to using AccessShareLock. Also, postpone closing the relation,so that we needn't copy its tupdesc. Also, fix unsafe use ofatt_isnull() for attributes past the end of the tuple.Per testing with a patch that complains if we open a relation withoutholding any lock on it. I don't plan to back-patch that patch, but weshould close the holes it identifies in all supported branches.Discussion:https://postgr.es/m/2038.1538335244@sss.pgh.pa.us
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‎contrib/pageinspect/heapfuncs.c

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -296,9 +296,8 @@ tuple_data_split_internal(Oid relid, char *tupdata,
296296
TupleDesctupdesc;
297297

298298
/* Get tuple descriptor from relation OID */
299-
rel=relation_open(relid,NoLock);
300-
tupdesc=CreateTupleDescCopyConstr(rel->rd_att);
301-
relation_close(rel,NoLock);
299+
rel=relation_open(relid,AccessShareLock);
300+
tupdesc=RelationGetDescr(rel);
302301

303302
raw_attrs=initArrayResult(BYTEAOID,CurrentMemoryContext, false);
304303
nattrs=tupdesc->natts;
@@ -315,7 +314,6 @@ tuple_data_split_internal(Oid relid, char *tupdata,
315314
bytea*attr_data=NULL;
316315

317316
attr=tupdesc->attrs[i];
318-
is_null= (t_infomask&HEAP_HASNULL)&&att_isnull(i,t_bits);
319317

320318
/*
321319
* Tuple header can specify less attributes than tuple descriptor as
@@ -325,6 +323,8 @@ tuple_data_split_internal(Oid relid, char *tupdata,
325323
*/
326324
if (i >= (t_infomask2&HEAP_NATTS_MASK))
327325
is_null= true;
326+
else
327+
is_null= (t_infomask&HEAP_HASNULL)&&att_isnull(i,t_bits);
328328

329329
if (!is_null)
330330
{
@@ -384,6 +384,8 @@ tuple_data_split_internal(Oid relid, char *tupdata,
384384
(errcode(ERRCODE_DATA_CORRUPTED),
385385
errmsg("end of tuple reached without looking at all its data")));
386386

387+
relation_close(rel,AccessShareLock);
388+
387389
returnmakeArrayResult(raw_attrs,CurrentMemoryContext);
388390
}
389391

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