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

Browse Source 
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
This commit is contained in:
Tom Lane
2018-08-15 16:29:31 -04:00
parent 805889d7d2
commit cc4f6b7786
8 changed files with 47 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
src/test/isolation/isolation_main.c
View File

@ -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);

2
src/test/regress/pg_regress.c
View File

@ -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

28
src/test/regress/pg_regress_main.c
View File

@ -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)