Fix out-of-bound memory access for interval -> char conversion

Using Roman numbers (via "RM" or "rm") for a conversion to calculate a
number of months has never considered the case of negative numbers,
where a conversion could easily cause out-of-bound memory accesses.  The
conversions in themselves were not completely consistent either, as
specifying 12 would result in NULL, but it should mean XII.

This commit reworks the conversion calculation to have a more
consistent behavior:
- If the number of months and years is 0, return NULL.
- If the number of months is positive, return the exact month number.
- If the number of months is negative, do a backward calculation, with
-1 meaning December, -2 November, etc.

Reported-by: Theodor Arsenij Larionov-Trichkin
Author: Julien Rouhaud
Discussion: https://postgr.es/m/16953-f255a18f8c51f1d5@postgresql.org
backpatch-through: 9.6

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 5c54823efde9117d778207139c8a1d108418f3e8..42792b7f0b6f8aa5846fd2addbec057382e1fcf7 100644 (file)
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -2973,18 +2973,61 @@ DCH_to_char(FormatNode *node, bool is_interval, TmToChar *in, char *out, Oid col
                s += strlen(s);
                break;
            case DCH_RM:
-               if (!tm->tm_mon)
-                   break;
-               sprintf(s, "%*s", S_FM(n->suffix) ? 0 : -4,
-                       rm_months_upper[MONTHS_PER_YEAR - tm->tm_mon]);
-               s += strlen(s);
-               break;
+               /* FALLTHROUGH */
            case DCH_rm:
-               if (!tm->tm_mon)
+
+               /*
+                * For intervals, values like '12 month' will be reduced to 0
+                * month and some years.  These should be processed.
+                */
+               if (!tm->tm_mon && !tm->tm_year)
                    break;
-               sprintf(s, "%*s", S_FM(n->suffix) ? 0 : -4,
-                       rm_months_lower[MONTHS_PER_YEAR - tm->tm_mon]);
-               s += strlen(s);
+               else
+               {
+                   int         mon = 0;
+                   const char *const *months;
+
+                   if (n->key->id == DCH_RM)
+                       months = rm_months_upper;
+                   else
+                       months = rm_months_lower;
+
+                   /*
+                    * Compute the position in the roman-numeral array.  Note
+                    * that the contents of the array are reversed, December
+                    * being first and January last.
+                    */
+                   if (tm->tm_mon == 0)
+                   {
+                       /*
+                        * This case is special, and tracks the case of full
+                        * interval years.
+                        */
+                       mon = tm->tm_year >= 0 ? 0 : MONTHS_PER_YEAR - 1;
+                   }
+                   else if (tm->tm_mon < 0)
+                   {
+                       /*
+                        * Negative case.  In this case, the calculation is
+                        * reversed, where -1 means December, -2 November,
+                        * etc.
+                        */
+                       mon = -1 * (tm->tm_mon + 1);
+                   }
+                   else
+                   {
+                       /*
+                        * Common case, with a strictly positive value.  The
+                        * position in the array matches with the value of
+                        * tm_mon.
+                        */
+                       mon = MONTHS_PER_YEAR - tm->tm_mon;
+                   }
+
+                   sprintf(s, "%*s", S_FM(n->suffix) ? 0 : -4,
+                           months[mon]);
+                   s += strlen(s);
+               }
                break;
            case DCH_W:
                sprintf(s, "%d", (tm->tm_mday - 1) / 7 + 1);

diff --git a/src/test/regress/expected/timestamp.out b/src/test/regress/expected/timestamp.out
index ba27d9e2c5d736ca0e42ba9c37635c95f982ea5c..3025d8431e08aa844151477748f860a9fadf9848 100644 (file)
--- a/src/test/regress/expected/timestamp.out
+++ b/src/test/regress/expected/timestamp.out
@@ -1688,6 +1688,42 @@ SELECT '' AS to_char_11, to_char(d1, 'FMIYYY FMIYY FMIY FMI FMIW FMIDDD FMID')
             | 2001 1 1 1 1 1 1
 (65 rows)
 
+-- Roman months, with upper and lower case.
+SELECT i,
+       to_char(i * interval '1mon', 'rm'),
+       to_char(i * interval '1mon', 'RM')
+    FROM generate_series(-13, 13) i;
+  i  | to_char | to_char 
+-----+---------+---------
+ -13 | xii     | XII 
+ -12 | i       | I   
+ -11 | ii      | II  
+ -10 | iii     | III 
+  -9 | iv      | IV  
+  -8 | v       | V   
+  -7 | vi      | VI  
+  -6 | vii     | VII 
+  -5 | viii    | VIII
+  -4 | ix      | IX  
+  -3 | x       | X   
+  -2 | xi      | XI  
+  -1 | xii     | XII 
+   0 |         | 
+   1 | i       | I   
+   2 | ii      | II  
+   3 | iii     | III 
+   4 | iv      | IV  
+   5 | v       | V   
+   6 | vi      | VI  
+   7 | vii     | VII 
+   8 | viii    | VIII
+   9 | ix      | IX  
+  10 | x       | X   
+  11 | xi      | XI  
+  12 | xii     | XII 
+  13 | i       | I   
+(27 rows)
+
 -- timestamp numeric fields constructor
 SELECT make_timestamp(2014,12,28,6,30,45.887);
         make_timestamp        

diff --git a/src/test/regress/sql/timestamp.sql b/src/test/regress/sql/timestamp.sql
index 56d57848f9d9393c170685b903d16ca931242a71..55380c59e77b45a911610e04e0504ef905f44018 100644 (file)
--- a/src/test/regress/sql/timestamp.sql
+++ b/src/test/regress/sql/timestamp.sql
@@ -231,5 +231,11 @@ SELECT '' AS to_char_10, to_char(d1, 'IYYY IYY IY I IW IDDD ID')
 SELECT '' AS to_char_11, to_char(d1, 'FMIYYY FMIYY FMIY FMI FMIW FMIDDD FMID')
    FROM TIMESTAMP_TBL;
 
+-- Roman months, with upper and lower case.
+SELECT i,
+       to_char(i * interval '1mon', 'rm'),
+       to_char(i * interval '1mon', 'RM')
+    FROM generate_series(-13, 13) i;
+
 -- timestamp numeric fields constructor
 SELECT make_timestamp(2014,12,28,6,30,45.887);