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2b68f6caea
When an architecture fully supports randomizing the ELF load location, a per-arch mmap_rnd() function is used to find a randomized mmap base. In preparation for randomizing the location of ET_DYN binaries separately from mmap, this renames and exports these functions as arch_mmap_rnd(). Additionally introduces CONFIG_ARCH_HAS_ELF_RANDOMIZE for describing this feature on architectures that support it (which is a superset of ARCH_BINFMT_ELF_RANDOMIZE_PIE, since s390 already supports a separated ET_DYN ASLR from mmap ASLR without the ARCH_BINFMT_ELF_RANDOMIZE_PIE logic). Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Hector Marco-Gisbert <hecmargi@upv.es> Cc: Russell King <linux@arm.linux.org.uk> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: "David A. Long" <dave.long@linaro.org> Cc: Andrey Ryabinin <a.ryabinin@samsung.com> Cc: Arun Chandran <achandran@mvista.com> Cc: Yann Droneaud <ydroneaud@opteya.com> Cc: Min-Hua Chen <orca.chen@gmail.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Alex Smith <alex@alex-smith.me.uk> Cc: Markos Chandras <markos.chandras@imgtec.com> Cc: Vineeth Vijayan <vvijayan@mvista.com> Cc: Jeff Bailey <jeffbailey@google.com> Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Behan Webster <behanw@converseincode.com> Cc: Ismael Ripoll <iripoll@upv.es> Cc: Jan-Simon Mller <dl9pf@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
128 lines
3.2 KiB
C
128 lines
3.2 KiB
C
/*
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* Flexible mmap layout support
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*
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* Based on code by Ingo Molnar and Andi Kleen, copyrighted
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* as follows:
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*
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* Copyright 2003-2009 Red Hat Inc.
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* All Rights Reserved.
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* Copyright 2005 Andi Kleen, SUSE Labs.
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* Copyright 2007 Jiri Kosina, SUSE Labs.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program 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
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/personality.h>
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#include <linux/mm.h>
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#include <linux/random.h>
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#include <linux/limits.h>
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#include <linux/sched.h>
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#include <asm/elf.h>
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struct va_alignment __read_mostly va_align = {
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.flags = -1,
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};
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static unsigned long stack_maxrandom_size(void)
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{
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unsigned long max = 0;
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if ((current->flags & PF_RANDOMIZE) &&
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!(current->personality & ADDR_NO_RANDOMIZE)) {
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max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;
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}
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return max;
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}
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/*
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* Top of mmap area (just below the process stack).
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*
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* Leave an at least ~128 MB hole with possible stack randomization.
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*/
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#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
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#define MAX_GAP (TASK_SIZE/6*5)
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static int mmap_is_legacy(void)
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{
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if (current->personality & ADDR_COMPAT_LAYOUT)
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return 1;
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if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
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return 1;
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return sysctl_legacy_va_layout;
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}
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unsigned long arch_mmap_rnd(void)
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{
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unsigned long rnd;
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/*
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* 8 bits of randomness in 32bit mmaps, 20 address space bits
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* 28 bits of randomness in 64bit mmaps, 40 address space bits
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*/
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if (mmap_is_ia32())
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rnd = (unsigned long)get_random_int() % (1<<8);
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else
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rnd = (unsigned long)get_random_int() % (1<<28);
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return rnd << PAGE_SHIFT;
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}
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static unsigned long mmap_base(unsigned long rnd)
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{
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unsigned long gap = rlimit(RLIMIT_STACK);
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if (gap < MIN_GAP)
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gap = MIN_GAP;
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else if (gap > MAX_GAP)
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gap = MAX_GAP;
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return PAGE_ALIGN(TASK_SIZE - gap - rnd);
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}
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/*
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* Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
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* does, but not when emulating X86_32
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*/
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static unsigned long mmap_legacy_base(unsigned long rnd)
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{
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if (mmap_is_ia32())
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return TASK_UNMAPPED_BASE;
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else
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return TASK_UNMAPPED_BASE + rnd;
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}
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/*
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* This function, called very early during the creation of a new
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* process VM image, sets up which VM layout function to use:
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*/
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void arch_pick_mmap_layout(struct mm_struct *mm)
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{
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unsigned long random_factor = 0UL;
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if (current->flags & PF_RANDOMIZE)
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random_factor = arch_mmap_rnd();
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mm->mmap_legacy_base = mmap_legacy_base(random_factor);
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if (mmap_is_legacy()) {
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mm->mmap_base = mm->mmap_legacy_base;
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mm->get_unmapped_area = arch_get_unmapped_area;
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} else {
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mm->mmap_base = mmap_base(random_factor);
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mm->get_unmapped_area = arch_get_unmapped_area_topdown;
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}
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}
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