From d371efb39c33f79ad5f6741d76bfae54df21eb55 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 15 Aug 2018 16:29:32 -0400 Subject: 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 --- src/backend/postmaster/pgstat.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'src/backend/postmaster/pgstat.c') diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index 236ebadddda..9a9c51648bb 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -3768,7 +3768,7 @@ 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"); } -- cgit v1.2.3