Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

Started by Ranier Vilelaover 5 years ago9 messageshackers
Beta feature

Hackorum builds and tests every patch posted to the lists, not only commitfest submissions. This is Hackorum's own CI rather than the PostgreSQL project's, and it is still under testing - please report anything that looks wrong.

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You can run a PostgreSQL built from this patch straight from Docker, with no checkout and no build:

docker run --rm -p 5432:5432 ghcr.io/hackorum-dev/postgres-patch:t44278
psql -h localhost -U postgres

Built from patchset v7 (message #7), August 18, 2026 at 04:05 PM.

Every patchset is also pushed to a branch of our PostgreSQL fork, so you can check out the same tree CI built. Without a PostgreSQL checkout:

git clone --branch t44278_7 https://github.com/hackorum-dev/postgres.git

In a checkout you already have, add the fork once:

git remote add hackorum https://github.com/hackorum-dev/postgres.git

then, for this patchset and every later one:

git fetch hackorum t44278_7 && git checkout t44278_7

Patchset v7 (message #7) is on t44278_7

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#1Ranier Vilela
ranier.vf@gmail.com

Hi,

Possible pointer TupleDesc rettupdesc used not initialized?

if (!isNull) at line 4346 taking a true branch, the function
check_sql_fn_retval at line 4448 can use rettupdesc uninitialized.

regards,
Ranier Vilela

#2Mark Dilger
mark.dilger@enterprisedb.com
In reply to: Ranier Vilela (#1)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

On May 24, 2021, at 5:37 PM, Ranier Vilela <ranier.vf@gmail.com> wrote:

Hi,

Possible pointer TupleDesc rettupdesc used not initialized?

if (!isNull) at line 4346 taking a true branch, the function check_sql_fn_retval at line 4448 can use rettupdesc uninitialized.

Care to submit a patch?


Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

#3Ranier Vilela
ranier.vf@gmail.com
In reply to: Mark Dilger (#2)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

Em seg., 24 de mai. de 2021 às 22:42, Mark Dilger <
mark.dilger@enterprisedb.com> escreveu:

On May 24, 2021, at 5:37 PM, Ranier Vilela <ranier.vf@gmail.com> wrote:

Hi,

Possible pointer TupleDesc rettupdesc used not initialized?

if (!isNull) at line 4346 taking a true branch, the function

check_sql_fn_retval at line 4448 can use rettupdesc uninitialized.

Care to submit a patch?

Hi Mark, sorry but not.
I examined the code and I can't say what the correct value is for
rettupdesc.

regards,
Ranier Vilela

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#4Zhihong Yu
zyu@yugabyte.com
In reply to: Ranier Vilela (#3)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

On Mon, May 24, 2021 at 7:21 PM Ranier Vilela <ranier.vf@gmail.com> wrote:

Em seg., 24 de mai. de 2021 às 22:42, Mark Dilger <
mark.dilger@enterprisedb.com> escreveu:

On May 24, 2021, at 5:37 PM, Ranier Vilela <ranier.vf@gmail.com> wrote:

Hi,

Possible pointer TupleDesc rettupdesc used not initialized?

if (!isNull) at line 4346 taking a true branch, the function

check_sql_fn_retval at line 4448 can use rettupdesc uninitialized.

Care to submit a patch?

Hi Mark, sorry but not.
I examined the code and I can't say what the correct value is for
rettupdesc.

Hi,
It seems the following call would fill up value for rettupdesc :

functypclass = get_expr_result_type((Node *) fexpr, NULL, &rettupdesc);

Cheers

Show quoted text

regards,
Ranier Vilela

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#5Ranier Vilela
ranier.vf@gmail.com
In reply to: Zhihong Yu (#4)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

Em seg., 24 de mai. de 2021 às 23:35, Zhihong Yu <zyu@yugabyte.com>
escreveu:

On Mon, May 24, 2021 at 7:21 PM Ranier Vilela <ranier.vf@gmail.com> wrote:

Em seg., 24 de mai. de 2021 às 22:42, Mark Dilger <
mark.dilger@enterprisedb.com> escreveu:

On May 24, 2021, at 5:37 PM, Ranier Vilela <ranier.vf@gmail.com>

wrote:

Hi,

Possible pointer TupleDesc rettupdesc used not initialized?

if (!isNull) at line 4346 taking a true branch, the function

check_sql_fn_retval at line 4448 can use rettupdesc uninitialized.

Care to submit a patch?

Hi Mark, sorry but not.
I examined the code and I can't say what the correct value is for
rettupdesc.

Hi,
It seems the following call would fill up value for rettupdesc :

functypclass = get_expr_result_type((Node *) fexpr, NULL, &rettupdesc);

In short, do you suggest running half the else?
To do this, you need to fill fexpr correctly.
It will not always be a trivial solution.

regards,
Ranier Vilela

#6Tom Lane
tgl@sss.pgh.pa.us
In reply to: Ranier Vilela (#1)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

Ranier Vilela <ranier.vf@gmail.com> writes:

Possible pointer TupleDesc rettupdesc used not initialized?
if (!isNull) at line 4346 taking a true branch, the function
check_sql_fn_retval at line 4448 can use rettupdesc uninitialized.

This seems to have been introduced by the SQL-function-body patch.

After some study, I concluded that the reason we haven't noticed
is that the case is nearly unreachable: check_sql_fn_retval never
consults the rettupdesc unless the function result type is composite
and the tlist length is more than one --- and we eliminated the latter
case earlier in inline_function.

There is an exception, namely if the single tlist item fails to
be coercible to the output type, but that's hard to get to given
that it'd have been checked while defining the SQL-body function.
I did manage to reproduce a problem after turning off
check_function_bodies so I could create a broken function.

In any case, inline_function has no business assuming that
check_sql_fn_retval doesn't need a valid value.

The simplest way to fix this seems to be to move the code that
creates "fexpr" and calls get_expr_result_type, so that we always
do that even for SQL-body cases. We could alternatively use some
other way to obtain a result tupdesc in the SQL-body path; but
creating the dummy FuncExpr node is cheap enough that I don't
think it's worth contortions to avoid doing it.

regards, tom lane

#7Ranier Vilela
ranier.vf@gmail.com
In reply to: Tom Lane (#6)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

Em ter., 25 de mai. de 2021 às 13:09, Tom Lane <tgl@sss.pgh.pa.us> escreveu:

Ranier Vilela <ranier.vf@gmail.com> writes:

Possible pointer TupleDesc rettupdesc used not initialized?
if (!isNull) at line 4346 taking a true branch, the function
check_sql_fn_retval at line 4448 can use rettupdesc uninitialized.

This seems to have been introduced by the SQL-function-body patch.

After some study, I concluded that the reason we haven't noticed
is that the case is nearly unreachable: check_sql_fn_retval never
consults the rettupdesc unless the function result type is composite
and the tlist length is more than one --- and we eliminated the latter
case earlier in inline_function.

There is an exception, namely if the single tlist item fails to
be coercible to the output type, but that's hard to get to given
that it'd have been checked while defining the SQL-body function.
I did manage to reproduce a problem after turning off
check_function_bodies so I could create a broken function.

In any case, inline_function has no business assuming that
check_sql_fn_retval doesn't need a valid value.

The simplest way to fix this seems to be to move the code that
creates "fexpr" and calls get_expr_result_type, so that we always
do that even for SQL-body cases. We could alternatively use some
other way to obtain a result tupdesc in the SQL-body path; but
creating the dummy FuncExpr node is cheap enough that I don't
think it's worth contortions to avoid doing it.

Following the guidelines, I provided a patch.
But I did more than requested, removed redundant variable and reduced the
scope of two.

vcregress check pass fine.

regards,
Ranier Vilela

Attachments:

t44278_7
v1_fix_uninitialized_var_clauses.patchapplication/octet-stream; name=v1_fix_uninitialized_var_clauses.patchDownload+28-28
#8Tom Lane
tgl@sss.pgh.pa.us
In reply to: Ranier Vilela (#7)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

Ranier Vilela <ranier.vf@gmail.com> writes:

Following the guidelines, I provided a patch.

Oh, I already pushed a fix, thanks.

regards, tom lane

#9Ranier Vilela
ranier.vf@gmail.com
In reply to: Tom Lane (#8)
Re: Possible pointer var TupleDesc rettupdesc used not initialized (src/backend/optimizer/util/clauses.c)

Em ter., 25 de mai. de 2021 às 14:35, Tom Lane <tgl@sss.pgh.pa.us> escreveu:

Ranier Vilela <ranier.vf@gmail.com> writes:

Following the guidelines, I provided a patch.

Oh, I already pushed a fix, thanks.

No problem!

Thank you.

regards,
Ranier Vilela