From 278b4175c9d7dd47c1a3071554aac02add3b3c35 Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Sun, 23 Sep 2018 14:13:52 +0200 Subject: [PATCH] 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. --- ChangeLog | 9 +++++++++ lib/vasnprintf.c | 4 +++- tests/test-vasnprintf.c | 21 ++++++++++++++++++++- 3 files changed, 32 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index 4158be6da0..904a5185e0 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,12 @@ +2018-09-23 Bruno Haible + + 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. + 2018-09-19 Paul Eggert maint: mktime.c now shared with glibc diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c index 56ffbe308a..30d021b284 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; diff --git a/tests/test-vasnprintf.c b/tests/test-vasnprintf.c index 19731bc933..93d81d7041 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) -- 2.39.5