forked from pool/glibc
Andreas Schwab
71ba03d4de
- aarch64-static-pie.patch: fix static PIE start code for BTI (bsc#1179450, BZ #27068) - iconv-redundant-shift.patch: iconv: Accept redundant shift sequences in IBM1364 (CVE-2020-27618, bsc#1178386, BZ #26224) - iconv-ucs4-loop-bounds.patch: iconv: Fix incorrect UCS4 inner loop bounds (CVE-2020-29562, bsc#1179694, BZ #26923) - printf-long-double-non-normal.patch: x86: Harden printf against non-normal long double values (CVE-2020-29573, bsc#1179721, BZ #26649) - get-nprocs-cpu-online-parsing.patch: Fix parsing of /sys/devices/system/cpu/online (bsc#1180038, BZ #25859) OBS-URL: https://build.opensuse.org/request/show/856525 OBS-URL: https://build.opensuse.org/package/show/Base:System/glibc?expand=0&rev=574
125 lines
4.5 KiB
Diff
125 lines
4.5 KiB
Diff
From 681900d29683722b1cb0a8e565a0585846ec5a61 Mon Sep 17 00:00:00 2001
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From: Florian Weimer <fweimer@redhat.com>
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Date: Tue, 22 Sep 2020 19:07:48 +0200
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Subject: [PATCH] x86: Harden printf against non-normal long double values (bug
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26649)
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The behavior of isnan/__builtin_isnan on bit patterns that do not
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correspond to something that the CPU would produce from valid inputs
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is currently under-defined in the toolchain. (The GCC built-in and
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glibc disagree.)
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The isnan check in PRINTF_FP_FETCH in stdio-common/printf_fp.c
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assumes the GCC behavior that returns true for non-normal numbers
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which are not specified as NaN. (The glibc implementation returns
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false for such numbers.)
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At present, passing non-normal numbers to __mpn_extract_long_double
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causes this function to produce irregularly shaped multi-precision
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integers, triggering undefined behavior in __printf_fp_l.
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With GCC 10 and glibc 2.32, this behavior is not visible because
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__builtin_isnan is used, which avoids calling
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__mpn_extract_long_double in this case. This commit updates the
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implementation of __mpn_extract_long_double so that regularly shaped
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multi-precision integers are produced in this case, avoiding
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undefined behavior in __printf_fp_l.
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---
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sysdeps/x86/Makefile | 4 ++
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sysdeps/x86/ldbl2mpn.c | 8 ++++
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sysdeps/x86/tst-ldbl-nonnormal-printf.c | 52 +++++++++++++++++++++++++
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3 files changed, 64 insertions(+)
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create mode 100644 sysdeps/x86/tst-ldbl-nonnormal-printf.c
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Index: glibc-2.32/sysdeps/i386/ldbl2mpn.c
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===================================================================
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--- glibc-2.32.orig/sysdeps/i386/ldbl2mpn.c
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+++ glibc-2.32/sysdeps/i386/ldbl2mpn.c
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@@ -115,6 +115,14 @@ __mpn_extract_long_double (mp_ptr res_pt
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&& res_ptr[N - 1] == 0)
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/* Pseudo zero. */
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*expt = 0;
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+ else
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+ /* Unlike other floating point formats, the most significant bit
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+ is explicit and expected to be set for normal numbers. Set it
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+ in case it is cleared in the input. Otherwise, callers will
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+ not be able to produce the expected multi-precision integer
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+ layout by shifting. */
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+ res_ptr[N - 1] |= (mp_limb_t) 1 << (LDBL_MANT_DIG - 1
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+ - ((N - 1) * BITS_PER_MP_LIMB));
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return N;
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}
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Index: glibc-2.32/sysdeps/x86/Makefile
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===================================================================
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--- glibc-2.32.orig/sysdeps/x86/Makefile
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+++ glibc-2.32/sysdeps/x86/Makefile
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@@ -9,6 +9,10 @@ tests += tst-get-cpu-features tst-get-cp
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tests-static += tst-get-cpu-features-static
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endif
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+ifeq ($(subdir),math)
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+tests += tst-ldbl-nonnormal-printf
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+endif # $(subdir) == math
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+
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ifeq ($(subdir),setjmp)
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gen-as-const-headers += jmp_buf-ssp.sym
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sysdep_routines += __longjmp_cancel
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Index: glibc-2.32/sysdeps/x86/tst-ldbl-nonnormal-printf.c
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===================================================================
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--- /dev/null
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+++ glibc-2.32/sysdeps/x86/tst-ldbl-nonnormal-printf.c
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@@ -0,0 +1,52 @@
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+/* Test printf with x86-specific non-normal long double value.
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+ Copyright (C) 2020 Free Software Foundation, Inc.
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+
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <stdio.h>
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+#include <string.h>
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+#include <support/check.h>
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+
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+/* Fill the stack with non-zero values. This makes a crash in
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+ snprintf more likely. */
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+static void __attribute__ ((noinline, noclone))
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+fill_stack (void)
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+{
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+ char buffer[65536];
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+ memset (buffer, 0xc0, sizeof (buffer));
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+ asm ("" ::: "memory");
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+}
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+
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+static int
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+do_test (void)
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+{
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+ fill_stack ();
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+
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+ long double value;
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+ memcpy (&value, "\x00\x04\x00\x00\x00\x00\x00\x00\x00\x04", 10);
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+
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+ char buf[30];
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+ int ret = snprintf (buf, sizeof (buf), "%Lg", value);
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+ TEST_COMPARE (ret, strlen (buf));
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+ if (strcmp (buf, "nan") != 0)
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+ /* If snprintf does not recognize the non-normal number as a NaN,
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+ it has added the missing explicit MSB. */
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+ TEST_COMPARE_STRING (buf, "3.02201e-4624");
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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