Prevent datebsearch() from crashing on base == NULL && nel == 0.

Normally nel == 0 works okay because the initial value of "last" will be
less than "base"; but if "base" is zero then the calculation wraps around
and we have a very large (unsigned) value for "last", so that the loop can
be entered and we get a SIGSEGV on a bogus pointer.

This is certainly the proximate cause of the recent reports of Windows
builds crashing on 'infinity'::timestamp --- evidently, they're either not
setting an active timezonetktbl, or setting an empty one.  It's not yet
clear to me why it's only happening on Windows and not happening on any
buildfarm member.  But even if that's due to some bug elsewhere, it seems
wise for this function to not choke on the powerup values of
timezonetktbl/sztimezonetktbl.

I also changed the copy of this code in ecpglib, although I am not sure
whether it's exposed to a similar hazard.

Per report and stack trace from Richard Broersma.

diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index db0a6487acffef00013951a9e0ac5e85abf418c8..0a12a9b2e175a2acd7d13d0c877ed4ce2b533dc0 100644 (file)
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -3569,24 +3569,27 @@ DateTimeParseError(int dterr, const char *str, const char *datatype)
 static const datetkn *
 datebsearch(const char *key, const datetkn *base, int nel)
 {
-       const datetkn *last = base + nel - 1,
-                          *position;
-       int                     result;
-
-       while (last >= base)
+       if (nel > 0)
        {
-               position = base + ((last - base) >> 1);
-               result = key[0] - position->token[0];
-               if (result == 0)
+               const datetkn *last = base + nel - 1,
+                                  *position;
+               int                     result;
+
+               while (last >= base)
                {
-                       result = strncmp(key, position->token, TOKMAXLEN);
+                       position = base + ((last - base) >> 1);
+                       result = key[0] - position->token[0];
                        if (result == 0)
-                               return position;
+                       {
+                               result = strncmp(key, position->token, TOKMAXLEN);
+                               if (result == 0)
+                                       return position;
+                       }
+                       if (result < 0)
+                               last = position - 1;
+                       else
+                               base = position + 1;
                }
-               if (result < 0)
-                       last = position - 1;
-               else
-                       base = position + 1;
        }
        return NULL;
 }

diff --git a/src/interfaces/ecpg/pgtypeslib/dt_common.c b/src/interfaces/ecpg/pgtypeslib/dt_common.c
index da3224aae3176d1e3c6d305f461843273225e0b4..45f1f8affd578ee18824a582c5e9873121e79f12 100644 (file)
--- a/src/interfaces/ecpg/pgtypeslib/dt_common.c
+++ b/src/interfaces/ecpg/pgtypeslib/dt_common.c
@@ -512,24 +512,27 @@ char         *pgtypes_date_months[] = {"January", "February", "March", "April", "May"
 static datetkn *
 datebsearch(char *key, datetkn *base, unsigned int nel)
 {
-       datetkn    *last = base + nel - 1,
-                          *position;
-       int                     result;
-
-       while (last >= base)
+       if (nel > 0)
        {
-               position = base + ((last - base) >> 1);
-               result = key[0] - position->token[0];
-               if (result == 0)
+               datetkn    *last = base + nel - 1,
+                                  *position;
+               int                     result;
+
+               while (last >= base)
                {
-                       result = strncmp(key, position->token, TOKMAXLEN);
+                       position = base + ((last - base) >> 1);
+                       result = key[0] - position->token[0];
                        if (result == 0)
-                               return position;
+                       {
+                               result = strncmp(key, position->token, TOKMAXLEN);
+                               if (result == 0)
+                                       return position;
+                       }
+                       if (result < 0)
+                               last = position - 1;
+                       else
+                               base = position + 1;
                }
-               if (result < 0)
-                       last = position - 1;
-               else
-                       base = position + 1;
        }
        return NULL;
 }