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Commit71caf3c

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Fix handling of R/W expanded datums that are passed to SQL functions.
fmgr_sql must make expanded-datum arguments read-only, becauseit's possible that the function body will pass the argument tomore than one callee function. If one of those functions takesthe datum's R/W property as license to scribble on it, then latercallees will see an unexpected value, leading to wrong answers.From a performance standpoint, it'd be nice to skip this in thecommon case that the argument value is passed to only one callee.However, detecting that seems fairly hard, and certainly notsomething that I care to attempt in a back-patched bug fix.Per report from Adam Mackler. This has been broken since weinvented expanded datums, so back-patch to all supported branches.Discussion:https://postgr.es/m/WScDU5qfoZ7PB2gXwNqwGGgDPmWzz08VdydcPFLhOwUKZcdWbblbo-0Lku-qhuEiZoXJ82jpiQU4hOjOcrevYEDeoAvz6nR0IU4IHhXnaCA=@mackler.emailDiscussion:https://postgr.es/m/187436.1660143060@sss.pgh.pa.us
1 parent4bc493d commit71caf3c

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3 files changed

+48
-3
lines changed

3 files changed

+48
-3
lines changed

‎src/backend/executor/functions.c

Lines changed: 17 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -923,6 +923,7 @@ postquel_sub_params(SQLFunctionCachePtr fcache,
923923
if (nargs>0)
924924
{
925925
ParamListInfoparamLI;
926+
Oid*argtypes=fcache->pinfo->argtypes;
926927

927928
if (fcache->paramLI==NULL)
928929
{
@@ -939,10 +940,24 @@ postquel_sub_params(SQLFunctionCachePtr fcache,
939940
{
940941
ParamExternData*prm=&paramLI->params[i];
941942

942-
prm->value=fcinfo->args[i].value;
943+
/*
944+
* If an incoming parameter value is a R/W expanded datum, we
945+
* force it to R/O. We'd be perfectly entitled to scribble on it,
946+
* but the problem is that if the parameter is referenced more
947+
* than once in the function, earlier references might mutate the
948+
* value seen by later references, which won't do at all. We
949+
* could do better if we could be sure of the number of Param
950+
* nodes in the function's plans; but we might not have planned
951+
* all the statements yet, nor do we have plan tree walker
952+
* infrastructure. (Examining the parse trees is not good enough,
953+
* because of possible function inlining during planning.)
954+
*/
943955
prm->isnull=fcinfo->args[i].isnull;
956+
prm->value=MakeExpandedObjectReadOnly(fcinfo->args[i].value,
957+
prm->isnull,
958+
get_typlen(argtypes[i]));
944959
prm->pflags=0;
945-
prm->ptype=fcache->pinfo->argtypes[i];
960+
prm->ptype=argtypes[i];
946961
}
947962
}
948963
else

‎src/test/regress/expected/create_function_3.out

Lines changed: 18 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -340,9 +340,25 @@ SELECT * FROM voidtest5(3);
340340
-----------
341341
(0 rows)
342342

343+
-- Regression tests for bugs:
344+
-- Check that arguments that are R/W expanded datums aren't corrupted by
345+
-- multiple uses. This test knows that array_append() returns a R/W datum
346+
-- and will modify a R/W array input in-place. We use SETOF to prevent
347+
-- inlining of the SQL function.
348+
CREATE FUNCTION double_append(anyarray, anyelement) RETURNS SETOF anyarray
349+
LANGUAGE SQL IMMUTABLE AS
350+
$$ SELECT array_append($1, $2) || array_append($1, $2) $$;
351+
SELECT double_append(array_append(ARRAY[q1], q2), q3)
352+
FROM (VALUES(1,2,3), (4,5,6)) v(q1,q2,q3);
353+
double_append
354+
---------------
355+
{1,2,3,1,2,3}
356+
{4,5,6,4,5,6}
357+
(2 rows)
358+
343359
-- Cleanup
344360
DROP SCHEMA temp_func_test CASCADE;
345-
NOTICE: drop cascades to21 other objects
361+
NOTICE: drop cascades to22 other objects
346362
DETAIL: drop cascades to function functest_a_1(text,date)
347363
drop cascades to function functest_a_2(text[])
348364
drop cascades to function functest_a_3()
@@ -364,5 +380,6 @@ drop cascades to function voidtest2(integer,integer)
364380
drop cascades to function voidtest3(integer)
365381
drop cascades to function voidtest4(integer)
366382
drop cascades to function voidtest5(integer)
383+
drop cascades to function double_append(anyarray,anyelement)
367384
DROP USER regress_unpriv_user;
368385
RESET search_path;

‎src/test/regress/sql/create_function_3.sql

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -219,6 +219,19 @@ CREATE FUNCTION voidtest5(a int) RETURNS SETOF VOID LANGUAGE SQL AS
219219
$$SELECT generate_series(1, a) $$ STABLE;
220220
SELECT*FROM voidtest5(3);
221221

222+
-- Regression tests for bugs:
223+
224+
-- Check that arguments that are R/W expanded datums aren't corrupted by
225+
-- multiple uses. This test knows that array_append() returns a R/W datum
226+
-- and will modify a R/W array input in-place. We use SETOF to prevent
227+
-- inlining of the SQL function.
228+
CREATEFUNCTIONdouble_append(anyarray, anyelement) RETURNS SETOF anyarray
229+
LANGUAGE SQL IMMUTABLEAS
230+
$$SELECT array_append($1, $2)|| array_append($1, $2) $$;
231+
232+
SELECT double_append(array_append(ARRAY[q1], q2), q3)
233+
FROM (VALUES(1,2,3), (4,5,6)) v(q1,q2,q3);
234+
222235
-- Cleanup
223236
DROPSCHEMA temp_func_test CASCADE;
224237
DROPUSER regress_unpriv_user;

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