Clean up assorted misuses of snprintf()'s result value.

Fix a small number of places that were testing the result of snprintf()
but doing so incorrectly.  The right test for buffer overrun, per C99,
is "result >= bufsize" not "result > bufsize".  Some places were also
checking for failure with "result == -1", but the standard only says
that a negative value is delivered on failure.

(Note that this only makes these places correct if snprintf() delivers
C99-compliant results.  But at least now these places are consistent
with all the other places where we assume that.)

Also, make psql_start_test() and isolation_start_test() check for
buffer overrun while constructing their shell commands.  There seems
like a higher risk of overrun, with more severe consequences, here
than there is for the individual file paths that are made elsewhere
in the same functions, so this seemed like a worthwhile change.

Also fix guc.c's do_serialize() to initialize errno = 0 before
calling vsnprintf.  In principle, this should be unnecessary because
vsnprintf should have set errno if it returns a failure indication ...
but the other two places this coding pattern is cribbed from don't
assume that, so let's be consistent.

These errors are all very old, so back-patch as appropriate.  I think
that only the shell command overrun cases are even theoretically
reachable in practice, but there's not much point in erroneous error
checks.

Discussion: https://postgr.es/m/17245.1534289329@sss.pgh.pa.us

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index a5d129129613710bd8135eacffa124248c53cf5d..8a5b2b3b420b72e242f246409919ffea89af1148 100644 (file)
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -4810,7 +4810,7 @@ get_dbstat_filename(bool permanent, bool tempname, Oid databaseid,
                                           pgstat_stat_directory,
                                           databaseid,
                                           tempname ? "tmp" : "stat");
-       if (printed > len)
+       if (printed >= len)
                elog(ERROR, "overlength pgstat path");
 }
 

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c5ba149996e0b13385c87501abcdb984cc2caa11..f458c0eeae86307090382e7b034d8099176eb1e6 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9441,6 +9441,8 @@ do_serialize(char **destptr, Size *maxbytes, const char *fmt,...)
        if (*maxbytes <= 0)
                elog(ERROR, "not enough space to serialize GUC state");
 
+       errno = 0;
+
        va_start(vargs, fmt);
        n = vsnprintf(*destptr, *maxbytes, fmt, vargs);
        va_end(vargs);

diff --git a/src/common/ip.c b/src/common/ip.c
index caca7be9e574ff6befbe637ed708fcac77f8f27f..002260ed5a06e2223c69706df12d9f1e4b43fd6a 100644 (file)
--- a/src/common/ip.c
+++ b/src/common/ip.c
@@ -233,7 +233,7 @@ getnameinfo_unix(const struct sockaddr_un *sa, int salen,
                                 char *service, int servicelen,
                                 int flags)
 {
-       int                     ret = -1;
+       int                     ret;
 
        /* Invalid arguments. */
        if (sa == NULL || sa->sun_family != AF_UNIX ||
@@ -243,14 +243,14 @@ getnameinfo_unix(const struct sockaddr_un *sa, int salen,
        if (node)
        {
                ret = snprintf(node, nodelen, "%s", "[local]");
-               if (ret == -1 || ret > nodelen)
+               if (ret < 0 || ret >= nodelen)
                        return EAI_MEMORY;
        }
 
        if (service)
        {
                ret = snprintf(service, servicelen, "%s", sa->sun_path);
-               if (ret == -1 || ret > servicelen)
+               if (ret < 0 || ret >= servicelen)
                        return EAI_MEMORY;
        }
 

diff --git a/src/interfaces/ecpg/pgtypeslib/common.c b/src/interfaces/ecpg/pgtypeslib/common.c
index c5d1621ff1effbdd53a43c3e22e0d68c7dab33ed..a8a7e02be035aacfe8ccb772764b4b9ffbf2b054 100644 (file)
--- a/src/interfaces/ecpg/pgtypeslib/common.c
+++ b/src/interfaces/ecpg/pgtypeslib/common.c
@@ -110,7 +110,7 @@ pgtypes_fmt_replace(union un_fmt_comb replace_val, int replace_type, char **outp
                                                break;
                                }
 
-                               if (i < 0)
+                               if (i < 0 || i >= PGTYPES_FMT_NUM_MAX_DIGITS)
                                {
                                        free(t);
                                        return -1;

diff --git a/src/port/getaddrinfo.c b/src/port/getaddrinfo.c
index 21f1f1b94b64e22bea12a607eba429758ba7b893..1054d857b372d6c8f9c8bd7a0362218fa9c86b19 100644 (file)
--- a/src/port/getaddrinfo.c
+++ b/src/port/getaddrinfo.c
@@ -405,7 +405,7 @@ getnameinfo(const struct sockaddr *sa, int salen,
                        ret = snprintf(service, servicelen, "%d",
                                                   pg_ntoh16(((struct sockaddr_in *) sa)->sin_port));
                }
-               if (ret == -1 || ret >= servicelen)
+               if (ret < 0 || ret >= servicelen)
                        return EAI_MEMORY;
        }
 

diff --git a/src/test/isolation/isolation_main.c b/src/test/isolation/isolation_main.c
index 58402b74d803f7b7a51bb1af6092ebe92d1629c2..d3ada6d2bcf77953fef162fc73c7f9b02e672915 100644 (file)
--- a/src/test/isolation/isolation_main.c
+++ b/src/test/isolation/isolation_main.c
@@ -75,15 +75,27 @@ isolation_start_test(const char *testname,
        add_stringlist_item(expectfiles, expectfile);
 
        if (launcher)
+       {
                offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
                                                   "%s ", launcher);
+               if (offset >= sizeof(psql_cmd))
+               {
+                       fprintf(stderr, _("command too long\n"));
+                       exit(2);
+               }
+       }
 
-       snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
-                        "\"%s\" \"dbname=%s\" < \"%s\" > \"%s\" 2>&1",
-                        isolation_exec,
-                        dblist->str,
-                        infile,
-                        outfile);
+       offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
+                                          "\"%s\" \"dbname=%s\" < \"%s\" > \"%s\" 2>&1",
+                                          isolation_exec,
+                                          dblist->str,
+                                          infile,
+                                          outfile);
+       if (offset >= sizeof(psql_cmd))
+       {
+               fprintf(stderr, _("command too long\n"));
+               exit(2);
+       }
 
        pid = spawn_process(psql_cmd);
 

diff --git a/src/test/regress/pg_regress.c b/src/test/regress/pg_regress.c
index 2ff2acc641b9387ada7c77720f09fdf55ea8a028..6890678fa81265887ca5a2fb060b57f61b9b1248 100644 (file)
--- a/src/test/regress/pg_regress.c
+++ b/src/test/regress/pg_regress.c
@@ -1024,7 +1024,7 @@ config_sspi_auth(const char *pgdata)
        } while (0)
 
        res = snprintf(fname, sizeof(fname), "%s/pg_hba.conf", pgdata);
-       if (res < 0 || res >= sizeof(fname) - 1)
+       if (res < 0 || res >= sizeof(fname))
        {
                /*
                 * Truncating this name is a fatal error, because we must not fail to

diff --git a/src/test/regress/pg_regress_main.c b/src/test/regress/pg_regress_main.c
index a2bd6a2cd5789b9fe37ce3051ac057307189fbf2..bd613e4fda19bd3ce5831615a920553b4892ebec 100644 (file)
--- a/src/test/regress/pg_regress_main.c
+++ b/src/test/regress/pg_regress_main.c
@@ -63,20 +63,32 @@ psql_start_test(const char *testname,
        add_stringlist_item(expectfiles, expectfile);
 
        if (launcher)
+       {
                offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
                                                   "%s ", launcher);
+               if (offset >= sizeof(psql_cmd))
+               {
+                       fprintf(stderr, _("command too long\n"));
+                       exit(2);
+               }
+       }
+
+       offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
+                                          "\"%s%spsql\" -X -a -q -d \"%s\" < \"%s\" > \"%s\" 2>&1",
+                                          bindir ? bindir : "",
+                                          bindir ? "/" : "",
+                                          dblist->str,
+                                          infile,
+                                          outfile);
+       if (offset >= sizeof(psql_cmd))
+       {
+               fprintf(stderr, _("command too long\n"));
+               exit(2);
+       }
 
        appnameenv = psprintf("PGAPPNAME=pg_regress/%s", testname);
        putenv(appnameenv);
 
-       snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
-                        "\"%s%spsql\" -X -a -q -d \"%s\" < \"%s\" > \"%s\" 2>&1",
-                        bindir ? bindir : "",
-                        bindir ? "/" : "",
-                        dblist->str,
-                        infile,
-                        outfile);
-
        pid = spawn_process(psql_cmd);
 
        if (pid == INVALID_PID)