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190 lines
4.7 KiB
190 lines
4.7 KiB
// SPDX-License-Identifier: GPL-2.0+ |
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/* |
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* flexible mmap layout support |
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* |
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* Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. |
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* All Rights Reserved. |
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* |
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* Started by Ingo Molnar <[email protected]> |
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*/ |
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#include <linux/elf-randomize.h> |
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#include <linux/personality.h> |
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#include <linux/mm.h> |
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#include <linux/mman.h> |
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#include <linux/sched/signal.h> |
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#include <linux/sched/mm.h> |
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#include <linux/random.h> |
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#include <linux/compat.h> |
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#include <linux/security.h> |
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#include <asm/elf.h> |
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static unsigned long stack_maxrandom_size(void) |
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{ |
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if (!(current->flags & PF_RANDOMIZE)) |
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return 0; |
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return STACK_RND_MASK << PAGE_SHIFT; |
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} |
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static inline int mmap_is_legacy(struct rlimit *rlim_stack) |
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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 (rlim_stack->rlim_cur == 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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return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT; |
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} |
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static unsigned long mmap_base_legacy(unsigned long rnd) |
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{ |
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return TASK_UNMAPPED_BASE + rnd; |
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} |
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static inline unsigned long mmap_base(unsigned long rnd, |
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struct rlimit *rlim_stack) |
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{ |
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unsigned long gap = rlim_stack->rlim_cur; |
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unsigned long pad = stack_maxrandom_size() + stack_guard_gap; |
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unsigned long gap_min, gap_max; |
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/* Values close to RLIM_INFINITY can overflow. */ |
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if (gap + pad > gap) |
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gap += pad; |
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/* |
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* Top of mmap area (just below the process stack). |
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* Leave at least a ~32 MB hole. |
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*/ |
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gap_min = 32 * 1024 * 1024UL; |
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gap_max = (STACK_TOP / 6) * 5; |
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if (gap < gap_min) |
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gap = gap_min; |
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else if (gap > gap_max) |
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gap = gap_max; |
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return PAGE_ALIGN(STACK_TOP - gap - rnd); |
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} |
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unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, |
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unsigned long len, unsigned long pgoff, |
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unsigned long flags) |
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{ |
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struct mm_struct *mm = current->mm; |
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struct vm_area_struct *vma; |
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struct vm_unmapped_area_info info; |
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if (len > TASK_SIZE - mmap_min_addr) |
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return -ENOMEM; |
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if (flags & MAP_FIXED) |
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goto check_asce_limit; |
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if (addr) { |
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addr = PAGE_ALIGN(addr); |
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vma = find_vma(mm, addr); |
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if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && |
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(!vma || addr + len <= vm_start_gap(vma))) |
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goto check_asce_limit; |
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} |
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info.flags = 0; |
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info.length = len; |
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info.low_limit = mm->mmap_base; |
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info.high_limit = TASK_SIZE; |
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if (filp || (flags & MAP_SHARED)) |
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info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT; |
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else |
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info.align_mask = 0; |
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info.align_offset = pgoff << PAGE_SHIFT; |
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addr = vm_unmapped_area(&info); |
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if (offset_in_page(addr)) |
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return addr; |
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check_asce_limit: |
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return check_asce_limit(mm, addr, len); |
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} |
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unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, |
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unsigned long len, unsigned long pgoff, |
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unsigned long flags) |
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{ |
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struct vm_area_struct *vma; |
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struct mm_struct *mm = current->mm; |
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struct vm_unmapped_area_info info; |
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/* requested length too big for entire address space */ |
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if (len > TASK_SIZE - mmap_min_addr) |
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return -ENOMEM; |
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if (flags & MAP_FIXED) |
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goto check_asce_limit; |
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/* requesting a specific address */ |
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if (addr) { |
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addr = PAGE_ALIGN(addr); |
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vma = find_vma(mm, addr); |
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if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && |
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(!vma || addr + len <= vm_start_gap(vma))) |
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goto check_asce_limit; |
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} |
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info.flags = VM_UNMAPPED_AREA_TOPDOWN; |
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info.length = len; |
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info.low_limit = max(PAGE_SIZE, mmap_min_addr); |
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info.high_limit = mm->mmap_base; |
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if (filp || (flags & MAP_SHARED)) |
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info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT; |
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else |
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info.align_mask = 0; |
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info.align_offset = pgoff << PAGE_SHIFT; |
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addr = vm_unmapped_area(&info); |
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/* |
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* A failed mmap() very likely causes application failure, |
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* so fall back to the bottom-up function here. This scenario |
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* can happen with large stack limits and large mmap() |
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* allocations. |
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*/ |
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if (offset_in_page(addr)) { |
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VM_BUG_ON(addr != -ENOMEM); |
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info.flags = 0; |
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info.low_limit = TASK_UNMAPPED_BASE; |
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info.high_limit = TASK_SIZE; |
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addr = vm_unmapped_area(&info); |
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if (offset_in_page(addr)) |
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return addr; |
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} |
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check_asce_limit: |
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return check_asce_limit(mm, addr, len); |
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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, struct rlimit *rlim_stack) |
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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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/* |
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* Fall back to the standard layout if the personality |
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* bit is set, or if the expected stack growth is unlimited: |
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*/ |
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if (mmap_is_legacy(rlim_stack)) { |
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mm->mmap_base = mmap_base_legacy(random_factor); |
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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, rlim_stack); |
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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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