From 4868e4468590bc32f9c3afed4ec795d6a7732c9d Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Wed, 3 Oct 2018 13:02:25 -0700 Subject: [PATCH] Ensure that snprintf.c's fmtint() doesn't overflow when printing INT64_MIN. This isn't actually a live bug, as the output happens to be the same. But it upsets tools like UBSan, which makes it worthwhile to fix. As it's an issue without practical consequences, don't backpatch. Author: Andres Freund Discussion: https://postgr.es/m/20180928001121.hhx5n6dsygqxr5wu@alap3.anarazel.de --- src/port/snprintf.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/src/port/snprintf.c b/src/port/snprintf.c index 3bd598d75c6..872d8001240 100644 --- a/src/port/snprintf.c +++ b/src/port/snprintf.c @@ -1007,6 +1007,7 @@ fmtint(long long value, char type, int forcesign, int leftjust, PrintfTarget *target) { unsigned long long base; + unsigned long long uvalue; int dosign; const char *cvt = "0123456789abcdef"; int signvalue = 0; @@ -1045,7 +1046,9 @@ fmtint(long long value, char type, int forcesign, int leftjust, /* Handle +/- */ if (dosign && adjust_sign((value < 0), forcesign, &signvalue)) - value = -value; + uvalue = -(uint64) value; + else + uvalue = (uint64) value; /* * SUS: the result of converting 0 with an explicit precision of 0 is no @@ -1056,8 +1059,6 @@ fmtint(long long value, char type, int forcesign, int leftjust, else { /* make integer string */ - unsigned long long uvalue = (unsigned long long) value; - do { convert[sizeof(convert) - (++vallen)] = cvt[uvalue % base];