From 442dbd6698282faafc0b83363cecf818cf88a9b6 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 10 Aug 2022 13:37:25 -0400 Subject: [PATCH] Fix handling of R/W expanded datums that are passed to SQL functions. fmgr_sql must make expanded-datum arguments read-only, because it's possible that the function body will pass the argument to more than one callee function. If one of those functions takes the datum's R/W property as license to scribble on it, then later callees will see an unexpected value, leading to wrong answers. From a performance standpoint, it'd be nice to skip this in the common case that the argument value is passed to only one callee. However, detecting that seems fairly hard, and certainly not something that I care to attempt in a back-patched bug fix. Per report from Adam Mackler. This has been broken since we invented expanded datums, so back-patch to all supported branches. Discussion: https://postgr.es/m/WScDU5qfoZ7PB2gXwNqwGGgDPmWzz08VdydcPFLhOwUKZcdWbblbo-0Lku-qhuEiZoXJ82jpiQU4hOjOcrevYEDeoAvz6nR0IU4IHhXnaCA=@mackler.email Discussion: https://postgr.es/m/187436.1660143060@sss.pgh.pa.us --- src/backend/executor/functions.c | 19 +++++++++++++++++-- .../regress/expected/create_function_3.out | 18 +++++++++++++++++- src/test/regress/sql/create_function_3.sql | 13 +++++++++++++ 3 files changed, 47 insertions(+), 3 deletions(-) diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c index 23545896d4..f63c8124e6 100644 --- a/src/backend/executor/functions.c +++ b/src/backend/executor/functions.c @@ -906,6 +906,7 @@ postquel_sub_params(SQLFunctionCachePtr fcache, if (nargs > 0) { ParamListInfo paramLI; + Oid *argtypes = fcache->pinfo->argtypes; int i; if (fcache->paramLI == NULL) @@ -933,10 +934,24 @@ postquel_sub_params(SQLFunctionCachePtr fcache, { ParamExternData *prm = ¶mLI->params[i]; - prm->value = fcinfo->arg[i]; + /* + * If an incoming parameter value is a R/W expanded datum, we + * force it to R/O. We'd be perfectly entitled to scribble on it, + * but the problem is that if the parameter is referenced more + * than once in the function, earlier references might mutate the + * value seen by later references, which won't do at all. We + * could do better if we could be sure of the number of Param + * nodes in the function's plans; but we might not have planned + * all the statements yet, nor do we have plan tree walker + * infrastructure. (Examining the parse trees is not good enough, + * because of possible function inlining during planning.) + */ prm->isnull = fcinfo->argnull[i]; + prm->value = MakeExpandedObjectReadOnly(fcinfo->arg[i], + prm->isnull, + get_typlen(argtypes[i])); prm->pflags = 0; - prm->ptype = fcache->pinfo->argtypes[i]; + prm->ptype = argtypes[i]; } } else diff --git a/src/test/regress/expected/create_function_3.out b/src/test/regress/expected/create_function_3.out index 3301885fc8..6482e70a81 100644 --- a/src/test/regress/expected/create_function_3.out +++ b/src/test/regress/expected/create_function_3.out @@ -340,10 +340,26 @@ SELECT * FROM voidtest5(3); ----------- (0 rows) +-- Regression tests for bugs: +-- Check that arguments that are R/W expanded datums aren't corrupted by +-- multiple uses. This test knows that array_append() returns a R/W datum +-- and will modify a R/W array input in-place. We use SETOF to prevent +-- inlining of the SQL function. +CREATE FUNCTION double_append(anyarray, anyelement) RETURNS SETOF anyarray +LANGUAGE SQL IMMUTABLE AS +$$ SELECT array_append($1, $2) || array_append($1, $2) $$; +SELECT double_append(array_append(ARRAY[q1], q2), q3) + FROM (VALUES(1,2,3), (4,5,6)) v(q1,q2,q3); + double_append +--------------- + {1,2,3,1,2,3} + {4,5,6,4,5,6} +(2 rows) + -- Cleanup \set VERBOSITY terse \\ -- suppress cascade details DROP SCHEMA temp_func_test CASCADE; -NOTICE: drop cascades to 21 other objects +NOTICE: drop cascades to 22 other objects \set VERBOSITY default DROP USER regress_unpriv_user; RESET search_path; diff --git a/src/test/regress/sql/create_function_3.sql b/src/test/regress/sql/create_function_3.sql index 24bb900990..a2b83ef14b 100644 --- a/src/test/regress/sql/create_function_3.sql +++ b/src/test/regress/sql/create_function_3.sql @@ -219,6 +219,19 @@ CREATE FUNCTION voidtest5(a int) RETURNS SETOF VOID LANGUAGE SQL AS $$ SELECT generate_series(1, a) $$ STABLE; SELECT * FROM voidtest5(3); +-- Regression tests for bugs: + +-- Check that arguments that are R/W expanded datums aren't corrupted by +-- multiple uses. This test knows that array_append() returns a R/W datum +-- and will modify a R/W array input in-place. We use SETOF to prevent +-- inlining of the SQL function. +CREATE FUNCTION double_append(anyarray, anyelement) RETURNS SETOF anyarray +LANGUAGE SQL IMMUTABLE AS +$$ SELECT array_append($1, $2) || array_append($1, $2) $$; + +SELECT double_append(array_append(ARRAY[q1], q2), q3) + FROM (VALUES(1,2,3), (4,5,6)) v(q1,q2,q3); + -- Cleanup \set VERBOSITY terse \\ -- suppress cascade details DROP SCHEMA temp_func_test CASCADE;