postgres.git / summary / log / commit / refs

commit    b081fe4199b69dc561f7d31c6a82b3ad996f657f
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Tue Mar 14 23:17:31 2023 +0000
First released in: 16.0, 11.20, 12.15, 13.11, 14.8, 15.3

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


 src/backend/utils/adt/formatting.c    | 11 +++++++++--
 src/test/regress/expected/numeric.out |  6 ++++++
 src/test/regress/sql/numeric.sql      |  1 +
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index f3f4db5ef60..e6246dc44bd 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -5695,13 +5695,20 @@ 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;
 			}
diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out
index 2ac2c99b196..26930f4db47 100644
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -1929,6 +1929,12 @@ SELECT 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 to_char('100'::numeric, 'foo999');
  to_char 
diff --git a/src/test/regress/sql/numeric.sql b/src/test/regress/sql/numeric.sql
index 6e9e6145d03..2dddb586255 100644
--- a/src/test/regress/sql/numeric.sql
+++ b/src/test/regress/sql/numeric.sql
@@ -979,6 +979,7 @@ FROM v;
 SELECT to_char('100'::numeric, 'FM999.9');
 SELECT to_char('100'::numeric, 'FM999.');
 SELECT to_char('100'::numeric, 'FM999');
+SELECT to_char('12345678901'::float8, 'FM9999999999D9999900000000000000000');
 
 -- Check parsing of literal text in a format string
 SELECT to_char('100'::numeric, 'foo999');


[parent: a563c24c9574]