### File ldbl-96-rem-pio2l.patch of Package glibc.18276

From 9333498794cde1d5cca518badf79533a24114b6f Mon Sep 17 00:00:00 2001 From: Joseph Myers <joseph@codesourcery.com> Date: Wed, 12 Feb 2020 23:31:56 +0000 Subject: [PATCH] Avoid ldbl-96 stack corruption from range reduction of pseudo-zero (bug 25487). Bug 25487 reports stack corruption in ldbl-96 sinl on a pseudo-zero argument (an representation where all the significand bits, including the explicit high bit, are zero, but the exponent is not zero, which is not a valid representation for the long double type). Although this is not a valid long double representation, existing practice in this area (see bug 4586, originally marked invalid but subsequently fixed) is that we still seek to avoid invalid memory accesses as a result, in case of programs that treat arbitrary binary data as long double representations, although the invalid representations of the ldbl-96 format do not need to be consistently handled the same as any particular valid representation. This patch makes the range reduction detect pseudo-zero and unnormal representations that would otherwise go to __kernel_rem_pio2, and returns a NaN for them instead of continuing with the range reduction process. (Pseudo-zero and unnormal representations whose unbiased exponent is less than -1 have already been safely returned from the function before this point without going through the rest of range reduction.) Pseudo-zero representations would previously result in the value passed to __kernel_rem_pio2 being all-zero, which is definitely unsafe; unnormal representations would previously result in a value passed whose high bit is zero, which might well be unsafe since that is not a form of input expected by __kernel_rem_pio2. Tested for x86_64. --- sysdeps/ieee754/ldbl-96/Makefile | 3 +- sysdeps/ieee754/ldbl-96/e_rem_pio2l.c | 12 +++++++ sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c | 41 ++++++++++++++++++++++ 3 files changed, 55 insertions(+), 1 deletion(-) create mode 100644 sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c Index: glibc-2.26/sysdeps/ieee754/ldbl-96/Makefile =================================================================== --- glibc-2.26.orig/sysdeps/ieee754/ldbl-96/Makefile +++ glibc-2.26/sysdeps/ieee754/ldbl-96/Makefile @@ -17,5 +17,8 @@ # <http://www.gnu.org/licenses/>. ifeq ($(subdir),math) -tests += test-canonical-ldbl-96 test-totalorderl-ldbl-96 +tests += test-canonical-ldbl-96 test-totalorderl-ldbl-96 test-sinl-pseudo +ifeq ($(have-ssp),yes) +CFLAGS-test-sinl-pseudo.c += -fstack-protector-all endif +endif # $(subdir) == math Index: glibc-2.26/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c =================================================================== --- glibc-2.26.orig/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c +++ glibc-2.26/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c @@ -210,6 +210,18 @@ __ieee754_rem_pio2l (long double x, long return 0; } + if ((i0 & 0x80000000) == 0) + { + /* Pseudo-zero and unnormal representations are not valid + representations of long double. We need to avoid stack + corruption in __kernel_rem_pio2, which expects input in a + particular normal form, but those representations do not need + to be consistently handled like any particular floating-point + value. */ + y[1] = y[0] = __builtin_nanl (""); + return 0; + } + /* Split the 64 bits of the mantissa into three 24-bit integers stored in a double array. */ exp = j0 - 23; Index: glibc-2.26/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c =================================================================== --- /dev/null +++ glibc-2.26/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c @@ -0,0 +1,41 @@ +/* Test sinl for pseudo-zeros and unnormals for ldbl-96 (bug 25487). + Copyright (C) 2020 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <math.h> +#include <math_ldbl.h> +#include <stdint.h> + +static int +do_test (void) +{ + for (int i = 0; i < 64; i++) + { + uint64_t sig = i == 63 ? 0 : 1ULL << i; + long double ld; + SET_LDOUBLE_WORDS (ld, 0x4141, + sig >> 32, sig & 0xffffffffULL); + /* The requirement is that no stack overflow occurs when the + pseudo-zero or unnormal goes through range reduction. */ + volatile long double ldr; + ldr = sinl (ld); + (void) ldr; + } + return 0; +} + +#include <support/test-driver.c>