From 2c7d533d2593b87dde99836689b43465ee5852ee Mon Sep 17 00:00:00 2001 From: Dongkyun Son Date: Wed, 26 May 2021 17:18:14 +0900 Subject: [PATCH] [CVE-2018-17942] vasnprintf: Fix heap memory overrun bug. Reported by Ben Pfaff in . * lib/vasnprintf.c (convert_to_decimal): Allocate one more byte of memory. * tests/test-vasnprintf.c (test_function): Add another test. Change-Id: I9375c9f006d83bff07820a8c1fba251435a14faa Signed-off-by: Dongkyun Son --- lib/vasnprintf.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c index 3b441d0..48ef7a6 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; -- 2.7.4