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5ea80f76a5
This reverts commit df54d6fa54.
The commit isn't necessarily wrong, but because it recalculates the
random mmap_base every time, it seems to confuse user memory allocators
that expect contiguous mmap allocations even when the mmap address isn't
specified.
In particular, the MATLAB Java runtime seems to be unhappy. See
https://bugzilla.kernel.org/show_bug.cgi?id=60774
So we'll want to apply the random offset only once, and Radu has a patch
for that. Revert this older commit in order to apply the other one.
Reported-by: Jeff Shorey <shoreyjeff@gmail.com>
Cc: Radu Caragea <sinaelgl@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
123 lines
3.0 KiB
C
123 lines
3.0 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 __read_mostly va_alignment va_align = {
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.flags = -1,
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};
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static unsigned int stack_maxrandom_size(void)
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{
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unsigned int 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 = ((-1U) & 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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static unsigned long mmap_rnd(void)
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{
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unsigned long rnd = 0;
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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 (current->flags & PF_RANDOMIZE) {
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if (mmap_is_ia32())
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rnd = get_random_int() % (1<<8);
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else
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rnd = get_random_int() % (1<<28);
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}
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return rnd << PAGE_SHIFT;
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}
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static unsigned long mmap_base(void)
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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 - mmap_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(void)
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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 + mmap_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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if (mmap_is_legacy()) {
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mm->mmap_base = 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();
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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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