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Fix contrib/seg to be more wary of long input numbers.
seg stores the number of significant digits in an input number in a "char" field. If char is signed, and the input is more than 127 digits long, the count can read out as negative causing seg_out() to print garbage (or, if you're really unlucky, even crash). To fix, clamp the digit count to be not more than FLT_DIG. (In theory this loses some information about what the original input was, but it doesn't seem like useful information; it would not survive dump/restore in any case.) Also, in case there are stored values of the seg type containing bad data, add a clamp in seg_out's restore() subroutine. Per bug #17725 from Robins Tharakan. It's been like this forever, so back-patch to all supported branches. Discussion: https://postgr.es/m/17725-0a09313b67fbe86e@postgresql.org
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-7
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4 files changed

+33
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‎contrib/seg/expected/seg.out

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -256,6 +256,13 @@ SELECT '12.34567890123456'::seg AS seg;
256256
12.3457
257257
(1 row)
258258

259+
-- Same, with a very long input
260+
SELECT '12.3456789012345600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'::seg AS seg;
261+
seg
262+
---------
263+
12.3457
264+
(1 row)
265+
259266
-- Numbers with certainty indicators
260267
SELECT '~6.5'::seg AS seg;
261268
seg

‎contrib/seg/seg.c

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -927,9 +927,13 @@ restore(char *result, float val, int n)
927927

928928
/*
929929
* Put a cap on the number of significant digits to avoid garbage in the
930-
* output and ensure we don't overrun the result buffer.
930+
* output and ensure we don't overrun the result buffer. (n should not be
931+
* negative, but check to protect ourselves against corrupted data.)
931932
*/
932-
n = Min(n, FLT_DIG);
933+
if (n <= 0)
934+
n = FLT_DIG;
935+
else
936+
n = Min(n, FLT_DIG);
933937

934938
/* remember the sign */
935939
sign = (val < 0 ? 1 : 0);

‎contrib/seg/segparse.y

Lines changed: 17 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@
33

44
#include "postgres.h"
55

6+
#include <float.h>
67
#include <math.h>
78

89
#include "fmgr.h"
@@ -23,6 +24,8 @@
2324

2425
static float seg_atof(const char *value);
2526

27+
static int sig_digits(const char *value);
28+
2629
static char strbuf[25] = {
2730
'0', '0', '0', '0', '0',
2831
'0', '0', '0', '0', '0',
@@ -65,9 +68,9 @@ range: boundary PLUMIN deviation
6568
result->lower = $1.val - $3.val;
6669
result->upper = $1.val + $3.val;
6770
sprintf(strbuf, "%g", result->lower);
68-
result->l_sigd = Max(Min(6, significant_digits(strbuf)), Max($1.sigd, $3.sigd));
71+
result->l_sigd = Max(sig_digits(strbuf), Max($1.sigd, $3.sigd));
6972
sprintf(strbuf, "%g", result->upper);
70-
result->u_sigd = Max(Min(6, significant_digits(strbuf)), Max($1.sigd, $3.sigd));
73+
result->u_sigd = Max(sig_digits(strbuf), Max($1.sigd, $3.sigd));
7174
result->l_ext = '\0';
7275
result->u_ext = '\0';
7376
}
@@ -124,7 +127,7 @@ boundary: SEGFLOAT
124127
float val = seg_atof($1);
125128

126129
$$.ext = '\0';
127-
$$.sigd = significant_digits($1);
130+
$$.sigd = sig_digits($1);
128131
$$.val = val;
129132
}
130133
| EXTENSION SEGFLOAT
@@ -133,7 +136,7 @@ boundary: SEGFLOAT
133136
float val = seg_atof($2);
134137

135138
$$.ext = $1[0];
136-
$$.sigd = significant_digits($2);
139+
$$.sigd = sig_digits($2);
137140
$$.val = val;
138141
}
139142
;
@@ -144,7 +147,7 @@ deviation: SEGFLOAT
144147
float val = seg_atof($1);
145148

146149
$$.ext = '\0';
147-
$$.sigd = significant_digits($1);
150+
$$.sigd = sig_digits($1);
148151
$$.val = val;
149152
}
150153
;
@@ -161,5 +164,14 @@ seg_atof(const char *value)
161164
return DatumGetFloat4(datum);
162165
}
163166

167+
static int
168+
sig_digits(const char *value)
169+
{
170+
int n = significant_digits(value);
171+
172+
/* Clamp, to ensure value will fit in sigd fields */
173+
return Min(n, FLT_DIG);
174+
}
175+
164176

165177
#include "segscan.c"

‎contrib/seg/sql/seg.sql

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -60,6 +60,9 @@ SELECT '3.400e5'::seg AS seg;
6060
-- Digits truncated
6161
SELECT '12.34567890123456'::seg AS seg;
6262

63+
-- Same, with a very long input
64+
SELECT '12.3456789012345600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'::seg AS seg;
65+
6366
-- Numbers with certainty indicators
6467
SELECT '~6.5'::seg AS seg;
6568
SELECT '<6.5'::seg AS seg;

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