Andrew Geissler | 82c905d | 2020-04-13 13:39:40 -0500 | [diff] [blame] | 1 | From ce265ec5bc25ec35fba53807abac1b0c8469895e Mon Sep 17 00:00:00 2001 |
| 2 | From: Joseph Myers <joseph@codesourcery.com> |
| 3 | Date: Wed, 12 Feb 2020 23:31:56 +0000 |
| 4 | Subject: [PATCH] Avoid ldbl-96 stack corruption from range reduction of |
| 5 | |
| 6 | pseudo-zero (bug 25487). |
| 7 | |
| 8 | Bug 25487 reports stack corruption in ldbl-96 sinl on a pseudo-zero |
| 9 | argument (an representation where all the significand bits, including |
| 10 | the explicit high bit, are zero, but the exponent is not zero, which |
| 11 | is not a valid representation for the long double type). |
| 12 | |
| 13 | Although this is not a valid long double representation, existing |
| 14 | practice in this area (see bug 4586, originally marked invalid but |
| 15 | subsequently fixed) is that we still seek to avoid invalid memory |
| 16 | accesses as a result, in case of programs that treat arbitrary binary |
| 17 | data as long double representations, although the invalid |
| 18 | representations of the ldbl-96 format do not need to be consistently |
| 19 | handled the same as any particular valid representation. |
| 20 | |
| 21 | This patch makes the range reduction detect pseudo-zero and unnormal |
| 22 | representations that would otherwise go to __kernel_rem_pio2, and |
| 23 | returns a NaN for them instead of continuing with the range reduction |
| 24 | process. (Pseudo-zero and unnormal representations whose unbiased |
| 25 | exponent is less than -1 have already been safely returned from the |
| 26 | function before this point without going through the rest of range |
| 27 | reduction.) Pseudo-zero representations would previously result in |
| 28 | the value passed to __kernel_rem_pio2 being all-zero, which is |
| 29 | definitely unsafe; unnormal representations would previously result in |
| 30 | a value passed whose high bit is zero, which might well be unsafe |
| 31 | since that is not a form of input expected by __kernel_rem_pio2. |
| 32 | |
| 33 | Tested for x86_64. |
| 34 | |
| 35 | CVE: CVE-2020-10029 |
| 36 | Upstream-Status: Backport [https://sourceware.org/git/gitweb.cgi?p=glibc.git; |
| 37 | a=patch;h=9333498794cde1d5cca518badf79533a24114b6f] |
| 38 | Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com> |
| 39 | |
| 40 | --- |
| 41 | sysdeps/ieee754/ldbl-96/Makefile | 3 ++- |
| 42 | sysdeps/ieee754/ldbl-96/e_rem_pio2l.c | 12 +++++++++ |
| 43 | sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c | 41 ++++++++++++++++++++++++++++++ |
| 44 | 3 files changed, 55 insertions(+), 1 deletion(-) |
| 45 | create mode 100644 sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c |
| 46 | |
| 47 | diff --git a/sysdeps/ieee754/ldbl-96/Makefile b/sysdeps/ieee754/ldbl-96/Makefile |
| 48 | index b103254..052c1c7 100644 |
| 49 | --- a/sysdeps/ieee754/ldbl-96/Makefile |
| 50 | +++ b/sysdeps/ieee754/ldbl-96/Makefile |
| 51 | @@ -17,5 +17,6 @@ |
| 52 | # <https://www.gnu.org/licenses/>. |
| 53 | |
| 54 | ifeq ($(subdir),math) |
| 55 | -tests += test-canonical-ldbl-96 test-totalorderl-ldbl-96 |
| 56 | +tests += test-canonical-ldbl-96 test-totalorderl-ldbl-96 test-sinl-pseudo |
| 57 | +CFLAGS-test-sinl-pseudo.c += -fstack-protector-all |
| 58 | endif |
| 59 | diff --git a/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c b/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c |
| 60 | index 805de22..1aeccb4 100644 |
| 61 | --- a/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c |
| 62 | +++ b/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c |
| 63 | @@ -210,6 +210,18 @@ __ieee754_rem_pio2l (long double x, long double *y) |
| 64 | return 0; |
| 65 | } |
| 66 | |
| 67 | + if ((i0 & 0x80000000) == 0) |
| 68 | + { |
| 69 | + /* Pseudo-zero and unnormal representations are not valid |
| 70 | + representations of long double. We need to avoid stack |
| 71 | + corruption in __kernel_rem_pio2, which expects input in a |
| 72 | + particular normal form, but those representations do not need |
| 73 | + to be consistently handled like any particular floating-point |
| 74 | + value. */ |
| 75 | + y[1] = y[0] = __builtin_nanl (""); |
| 76 | + return 0; |
| 77 | + } |
| 78 | + |
| 79 | /* Split the 64 bits of the mantissa into three 24-bit integers |
| 80 | stored in a double array. */ |
| 81 | exp = j0 - 23; |
| 82 | diff --git a/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c b/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c |
| 83 | new file mode 100644 |
| 84 | index 0000000..f59b977 |
| 85 | --- /dev/null |
| 86 | +++ b/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c |
| 87 | @@ -0,0 +1,41 @@ |
| 88 | +/* Test sinl for pseudo-zeros and unnormals for ldbl-96 (bug 25487). |
| 89 | + Copyright (C) 2020 Free Software Foundation, Inc. |
| 90 | + This file is part of the GNU C Library. |
| 91 | + |
| 92 | + The GNU C Library is free software; you can redistribute it and/or |
| 93 | + modify it under the terms of the GNU Lesser General Public |
| 94 | + License as published by the Free Software Foundation; either |
| 95 | + version 2.1 of the License, or (at your option) any later version. |
| 96 | + |
| 97 | + The GNU C Library is distributed in the hope that it will be useful, |
| 98 | + but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 99 | + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 100 | + Lesser General Public License for more details. |
| 101 | + |
| 102 | + You should have received a copy of the GNU Lesser General Public |
| 103 | + License along with the GNU C Library; if not, see |
| 104 | + <https://www.gnu.org/licenses/>. */ |
| 105 | + |
| 106 | +#include <math.h> |
| 107 | +#include <math_ldbl.h> |
| 108 | +#include <stdint.h> |
| 109 | + |
| 110 | +static int |
| 111 | +do_test (void) |
| 112 | +{ |
| 113 | + for (int i = 0; i < 64; i++) |
| 114 | + { |
| 115 | + uint64_t sig = i == 63 ? 0 : 1ULL << i; |
| 116 | + long double ld; |
| 117 | + SET_LDOUBLE_WORDS (ld, 0x4141, |
| 118 | + sig >> 32, sig & 0xffffffffULL); |
| 119 | + /* The requirement is that no stack overflow occurs when the |
| 120 | + pseudo-zero or unnormal goes through range reduction. */ |
| 121 | + volatile long double ldr; |
| 122 | + ldr = sinl (ld); |
| 123 | + (void) ldr; |
| 124 | + } |
| 125 | + return 0; |
| 126 | +} |
| 127 | + |
| 128 | +#include <support/test-driver.c> |