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Fix corner case bug in numeric to_char() some more.

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The band-aid applied in commit f0bedf3e4 turns out to still need
some work: it made sure we didn't set Np->last_relevant too small
(to the left of the decimal point), but it didn't prevent setting
it too large (off the end of the partially-converted string).
This could result in fetching data beyond the end of the allocated
space, which with very bad luck could cause a SIGSEGV, though
I don't see any hazard of interesting memory disclosure.

Per bug #17839 from Thiago Nunes.  The bug's pretty ancient,
so back-patch to all supported versions.

Discussion: https://postgr.es/m/17839-aada50db24d7b0da@postgresql.org
This commit is contained in:
Tom Lane 2023-03-14 19:17:31 -04:00
parent 52e9a78165
commit 386a26023a
3 changed files with 16 additions and 2 deletions
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11
src/backend/utils/adt/formatting.c
View File

@ -5685,13 +5685,20 @@ NUM_processor(FormatNode *node, NUMDesc *Num, char *inout,
/*
* If any '0' specifiers are present, make sure we don't strip
* those digits.
* those digits. But don't advance last_relevant beyond the last
* character of the Np->number string, which is a hazard if the
* number got shortened due to precision limitations.
*/
if (Np->last_relevant && Np->Num->zero_end > Np->out_pre_spaces)
{
int last_zero_pos;
char *last_zero;
last_zero = Np->number + (Np->Num->zero_end - Np->out_pre_spaces);
/* note that Np->number cannot be zero-length here */
last_zero_pos = strlen(Np->number) - 1;
last_zero_pos = Min(last_zero_pos,
Np->Num->zero_end - Np->out_pre_spaces);
last_zero = Np->number + last_zero_pos;
if (Np->last_relevant < last_zero)
Np->last_relevant = last_zero;
}

6
src/test/regress/expected/numeric.out
View File

@ -1266,6 +1266,12 @@ SELECT '' AS to_char_26, to_char('100'::numeric, 'FM999');
| 100
(1 row)
SELECT to_char('12345678901'::float8, 'FM9999999999D9999900000000000000000');
to_char
-----------------
##########.####
(1 row)
-- Check parsing of literal text in a format string
SELECT '' AS to_char_27, to_char('100'::numeric, 'foo999');
to_char_27 | to_char

1
src/test/regress/sql/numeric.sql
View File

@ -799,6 +799,7 @@ SELECT '' AS to_char_23, to_char(val, '9.999EEEE') FROM num_data;
SELECT '' AS to_char_24, to_char('100'::numeric, 'FM999.9');
SELECT '' AS to_char_25, to_char('100'::numeric, 'FM999.');
SELECT '' AS to_char_26, to_char('100'::numeric, 'FM999');
SELECT to_char('12345678901'::float8, 'FM9999999999D9999900000000000000000');
-- Check parsing of literal text in a format string
SELECT '' AS to_char_27, to_char('100'::numeric, 'foo999');