From 278b4175c9d7dd47c1a3071554aac02add3b3c35 Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Sun, 23 Sep 2018 14:13:52 +0200 Subject: vasnprintf: Fix heap memory overrun bug. Reported by Ben Pfaff in . * lib/vasnprintf.c (convert_to_decimal): Allocate one more byte of memory. --- lib/vasnprintf.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c index 56ffbe3..30d021b 100644 --- a/lib/vasnprintf.c +++ b/lib/vasnprintf.c @@ -860,7 +860,9 @@ convert_to_decimal (mpn_t a, size_t extra_zeroes) size_t a_len = a.nlimbs; /* 0.03345 is slightly larger than log(2)/(9*log(10)). */ size_t c_len = 9 * ((size_t)(a_len * (GMP_LIMB_BITS * 0.03345f)) + 1); - char *c_ptr = (char *) malloc (xsum (c_len, extra_zeroes)); + /* We need extra_zeroes bytes for zeroes, followed by c_len bytes for the + digits of a, followed by 1 byte for the terminating NUL. */ + char *c_ptr = (char *) malloc (xsum (xsum (extra_zeroes, c_len), 1)); if (c_ptr != NULL) { char *d_ptr = c_ptr; -- cgit v1.1