From 875a98baebfca49e1ecdad28562ccaa2e57e9b3a Mon Sep 17 00:00:00 2001 From: JinWang An Date: Thu, 25 Feb 2021 13:06:17 +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: Ia26b9cf4ddc7fb15856dd283ad32d50e7204e046 Signed-off-by: JinWang An --- lib/vasnprintf.c | 4 +++- tests/test-vasnprintf.c | 21 ++++++++++++++++++++- 2 files changed, 23 insertions(+), 2 deletions(-) diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c index 5267b1b..9e3a477 100644 --- a/lib/vasnprintf.c +++ b/lib/vasnprintf.c @@ -849,7 +849,9 @@ 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; diff --git a/tests/test-vasnprintf.c b/tests/test-vasnprintf.c index 4cce0a9..671f0cd 100644 --- a/tests/test-vasnprintf.c +++ b/tests/test-vasnprintf.c @@ -53,7 +53,26 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...)) ASSERT (result != NULL); ASSERT (strcmp (result, "12345") == 0); ASSERT (length == 5); - if (size < 6) + if (size < 5 + 1) + ASSERT (result != buf); + ASSERT (memcmp (buf + size, &"DEADBEEF"[size], 8 - size) == 0); + if (result != buf) + free (result); + } + + /* Note: This test assumes IEEE 754 representation of 'double' floats. */ + for (size = 0; size <= 8; size++) + { + size_t length; + char *result; + + memcpy (buf, "DEADBEEF", 8); + length = size; + result = my_asnprintf (buf, &length, "%2.0f", 1.6314159265358979e+125); + ASSERT (result != NULL); + ASSERT (strcmp (result, "163141592653589790215729350939528493057529598899734151772468186268423257777068536614838678161083520756952076273094236944990208") == 0); + ASSERT (length == 126); + if (size < 126 + 1) ASSERT (result != buf); ASSERT (memcmp (buf + size, &"DEADBEEF"[size], 8 - size) == 0); if (result != buf) -- 2.7.4