postgres.git / summary / log / commit / refs
commit 5ccb77586955375167917c9910c0fc29cd3cfea5
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue Feb 27 18:27:38 2018 +0000
First released in: 11.0, 9.3.23, 9.4.18, 9.5.13, 9.6.9, 10.4
Prevent dangling-pointer access when update trigger returns old tuple.
A before-update row trigger may choose to return the "new" or "old" tuple
unmodified. ExecBRUpdateTriggers failed to consider the second
possibility, and would proceed to free the "old" tuple even if it was the
one returned, leading to subsequent access to already-deallocated memory.
In debug builds this reliably leads to an "invalid memory alloc request
size" failure; in production builds it might accidentally work, but data
corruption is also possible.
This is a very old bug. There are probably a couple of reasons it hasn't
been noticed up to now. It would be more usual to return NULL if one
wanted to suppress the update action; returning "old" is significantly less
efficient since the update will occur anyway. Also, none of the standard
PLs would ever cause this because they all returned freshly-manufactured
tuples even if they were just copying "old". But commit 4b93f5799 changed
that for plpgsql, making it possible to see the bug with a plpgsql trigger.
Still, this is certainly legal behavior for a trigger function, so it's
ExecBRUpdateTriggers's fault not plpgsql's.
It seems worth creating a test case that exercises returning "old" directly
with a C-language trigger; testing this through plpgsql seems unreliable
because its behavior might change again.
Report and fix by Rushabh Lathia; regression test case by me.
Back-patch to all supported branches.
Discussion: https://postgr.es/m/CAGPqQf1P4pjiNPrMof=P_16E-DFjt457j+nH2ex3=nBTew7tXw@mail.gmail.com
src/backend/commands/trigger.c | 2 +-
src/test/regress/expected/triggers.out | 26 ++++++++++++++++++++++++
src/test/regress/input/create_function_1.source | 5 +++++
src/test/regress/output/create_function_1.source | 4 ++++
src/test/regress/regress.c | 16 +++++++++++++++
src/test/regress/sql/triggers.sql | 16 +++++++++++++++
6 files changed, 68 insertions(+), 1 deletion(-)
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 63db1a8c548..7a07f28673a 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -2503,7 +2503,7 @@ ExecBRUpdateTriggers(EState *estate, EPQState *epqstate,
return NULL; /* "do nothing" */
}
}
- if (trigtuple != fdw_trigtuple)
+ if (trigtuple != fdw_trigtuple && trigtuple != newtuple)
heap_freetuple(trigtuple);
if (newtuple != slottuple)
diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out
index 6706021051a..6ca48dd9bb1 100644
--- a/src/test/regress/expected/triggers.out
+++ b/src/test/regress/expected/triggers.out
@@ -133,6 +133,32 @@ DROP TABLE fkeys2;
-- select count(*) from dup17 where x = 13;
--
-- DROP TABLE dup17;
+-- Check behavior when trigger returns unmodified trigtuple
+create table trigtest (f1 int, f2 text);
+create trigger trigger_return_old
+ before insert or delete or update on trigtest
+ for each row execute procedure trigger_return_old();
+insert into trigtest values(1, 'foo');
+select * from trigtest;
+ f1 | f2
+----+-----
+ 1 | foo
+(1 row)
+
+update trigtest set f2 = f2 || 'bar';
+select * from trigtest;
+ f1 | f2
+----+-----
+ 1 | foo
+(1 row)
+
+delete from trigtest;
+select * from trigtest;
+ f1 | f2
+----+----
+(0 rows)
+
+drop table trigtest;
create sequence ttdummy_seq increment 10 start 0 minvalue 0;
create table tttest (
price_id int4,
diff --git a/src/test/regress/input/create_function_1.source b/src/test/regress/input/create_function_1.source
index aef15182874..7a86d5218db 100644
--- a/src/test/regress/input/create_function_1.source
+++ b/src/test/regress/input/create_function_1.source
@@ -42,6 +42,11 @@ CREATE FUNCTION funny_dup17 ()
AS '@libdir@/regress@DLSUFFIX@'
LANGUAGE C;
+CREATE FUNCTION trigger_return_old ()
+ RETURNS trigger
+ AS '@libdir@/regress@DLSUFFIX@'
+ LANGUAGE C;
+
CREATE FUNCTION ttdummy ()
RETURNS trigger
AS '@libdir@/regress@DLSUFFIX@'
diff --git a/src/test/regress/output/create_function_1.source b/src/test/regress/output/create_function_1.source
index 9761d127e1f..57b461f46a6 100644
--- a/src/test/regress/output/create_function_1.source
+++ b/src/test/regress/output/create_function_1.source
@@ -39,6 +39,10 @@ CREATE FUNCTION funny_dup17 ()
RETURNS trigger
AS '@libdir@/regress@DLSUFFIX@'
LANGUAGE C;
+CREATE FUNCTION trigger_return_old ()
+ RETURNS trigger
+ AS '@libdir@/regress@DLSUFFIX@'
+ LANGUAGE C;
CREATE FUNCTION ttdummy ()
RETURNS trigger
AS '@libdir@/regress@DLSUFFIX@'
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index eaa35ec3fca..53fc0b7da7b 100644
--- a/src/test/regress/regress.c
+++ b/src/test/regress/regress.c
@@ -444,6 +444,22 @@ funny_dup17(PG_FUNCTION_ARGS)
return PointerGetDatum(tuple);
}
+PG_FUNCTION_INFO_V1(trigger_return_old);
+
+Datum
+trigger_return_old(PG_FUNCTION_ARGS)
+{
+ TriggerData *trigdata = (TriggerData *) fcinfo->context;
+ HeapTuple tuple;
+
+ if (!CALLED_AS_TRIGGER(fcinfo))
+ elog(ERROR, "trigger_return_old: not fired by trigger manager");
+
+ tuple = trigdata->tg_trigtuple;
+
+ return PointerGetDatum(tuple);
+}
+
#define TTDUMMY_INFINITY 999999
static SPIPlanPtr splan = NULL;
diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql
index 0ea2c314dee..c4ff1f3f80e 100644
--- a/src/test/regress/sql/triggers.sql
+++ b/src/test/regress/sql/triggers.sql
@@ -131,6 +131,22 @@ DROP TABLE fkeys2;
--
-- DROP TABLE dup17;
+-- Check behavior when trigger returns unmodified trigtuple
+create table trigtest (f1 int, f2 text);
+
+create trigger trigger_return_old
+ before insert or delete or update on trigtest
+ for each row execute procedure trigger_return_old();
+
+insert into trigtest values(1, 'foo');
+select * from trigtest;
+update trigtest set f2 = f2 || 'bar';
+select * from trigtest;
+delete from trigtest;
+select * from trigtest;
+
+drop table trigtest;
+
create sequence ttdummy_seq increment 10 start 0 minvalue 0;
create table tttest (
[parent: 5181bebba73b]