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From 6d059cebfdefbdf56910a858f8b603d37f10ef6d Mon Sep 17 00:00:00 2001
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From: Bruno Haible <bruno@clisp.org>
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Date: Sun, 23 Sep 2018 14:13:52 +0200
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Subject: [PATCH] vasnprintf: Fix heap memory overrun bug.
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Reported by Ben Pfaff <blp@cs.stanford.edu> in
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<https://lists.gnu.org/archive/html/bug-gnulib/2018-09/msg00107.html>.
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* lib/vasnprintf.c (convert_to_decimal): Allocate one more byte of
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memory.
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* tests/test-vasnprintf.c (test_function): Add another test.
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Upstream-commit: 278b4175c9d7dd47c1a3071554aac02add3b3c35
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Signed-off-by: Kamil Dudka <kdudka@redhat.com>
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---
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gnulib-tests/test-vasnprintf.c | 21 ++++++++++++++++++++-
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lib/vasnprintf.c | 4 +++-
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2 files changed, 23 insertions(+), 2 deletions(-)
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diff --git a/gnulib-tests/test-vasnprintf.c b/gnulib-tests/test-vasnprintf.c
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index 19731bc..93d81d7 100644
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--- a/gnulib-tests/test-vasnprintf.c
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+++ b/gnulib-tests/test-vasnprintf.c
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@@ -53,7 +53,26 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
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ASSERT (result != NULL);
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ASSERT (strcmp (result, "12345") == 0);
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ASSERT (length == 5);
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- if (size < 6)
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+ if (size < 5 + 1)
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+ ASSERT (result != buf);
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+ ASSERT (memcmp (buf + size, &"DEADBEEF"[size], 8 - size) == 0);
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+ if (result != buf)
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+ free (result);
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+ }
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+
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+ /* Note: This test assumes IEEE 754 representation of 'double' floats. */
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+ for (size = 0; size <= 8; size++)
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+ {
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+ size_t length;
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+ char *result;
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+
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+ memcpy (buf, "DEADBEEF", 8);
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+ length = size;
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+ result = my_asnprintf (buf, &length, "%2.0f", 1.6314159265358979e+125);
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+ ASSERT (result != NULL);
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+ ASSERT (strcmp (result, "163141592653589790215729350939528493057529598899734151772468186268423257777068536614838678161083520756952076273094236944990208") == 0);
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+ ASSERT (length == 126);
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+ if (size < 126 + 1)
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ASSERT (result != buf);
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ASSERT (memcmp (buf + size, &"DEADBEEF"[size], 8 - size) == 0);
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if (result != buf)
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diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c
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index 3b441d0..48ef7a6 100644
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--- a/lib/vasnprintf.c
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+++ b/lib/vasnprintf.c
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@@ -860,7 +860,9 @@ convert_to_decimal (mpn_t a, size_t extra_zeroes)
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size_t a_len = a.nlimbs;
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/* 0.03345 is slightly larger than log(2)/(9*log(10)). */
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size_t c_len = 9 * ((size_t)(a_len * (GMP_LIMB_BITS * 0.03345f)) + 1);
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- char *c_ptr = (char *) malloc (xsum (c_len, extra_zeroes));
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+ /* We need extra_zeroes bytes for zeroes, followed by c_len bytes for the
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+ digits of a, followed by 1 byte for the terminating NUL. */
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+ char *c_ptr = (char *) malloc (xsum (xsum (extra_zeroes, c_len), 1));
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if (c_ptr != NULL)
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{
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char *d_ptr = c_ptr;
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--
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2.17.1
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