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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * flexible mmap layout support
4 *
5 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
6 * All Rights Reserved.
7 *
8 * Started by Ingo Molnar <mingo@elte.hu>
9 */
10
11#include <linux/elf-randomize.h>
12#include <linux/personality.h>
13#include <linux/mm.h>
14#include <linux/mman.h>
15#include <linux/sched/signal.h>
16#include <linux/sched/mm.h>
17#include <linux/random.h>
18#include <linux/compat.h>
19#include <linux/security.h>
20#include <linux/hugetlb.h>
21#include <asm/elf.h>
22
23static unsigned long stack_maxrandom_size(void)
24{
25 if (!(current->flags & PF_RANDOMIZE))
26 return 0;
27 return STACK_RND_MASK << PAGE_SHIFT;
28}
29
30static inline int mmap_is_legacy(struct rlimit *rlim_stack)
31{
32 if (current->personality & ADDR_COMPAT_LAYOUT)
33 return 1;
34 if (rlim_stack->rlim_cur == RLIM_INFINITY)
35 return 1;
36 return sysctl_legacy_va_layout;
37}
38
39unsigned long arch_mmap_rnd(void)
40{
41 return (get_random_u32() & MMAP_RND_MASK) << PAGE_SHIFT;
42}
43
44static unsigned long mmap_base_legacy(unsigned long rnd)
45{
46 return TASK_UNMAPPED_BASE + rnd;
47}
48
49static inline unsigned long mmap_base(unsigned long rnd,
50 struct rlimit *rlim_stack)
51{
52 unsigned long gap = rlim_stack->rlim_cur;
53 unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
54 unsigned long gap_min, gap_max;
55
56 /* Values close to RLIM_INFINITY can overflow. */
57 if (gap + pad > gap)
58 gap += pad;
59
60 /*
61 * Top of mmap area (just below the process stack).
62 * Leave at least a ~128 MB hole.
63 */
64 gap_min = SZ_128M;
65 gap_max = (STACK_TOP / 6) * 5;
66
67 if (gap < gap_min)
68 gap = gap_min;
69 else if (gap > gap_max)
70 gap = gap_max;
71
72 return PAGE_ALIGN(STACK_TOP - gap - rnd);
73}
74
75static int get_align_mask(struct file *filp, unsigned long flags)
76{
77 if (filp && is_file_hugepages(filp))
78 return huge_page_mask_align(filp);
79 if (!(current->flags & PF_RANDOMIZE))
80 return 0;
81 if (filp || (flags & MAP_SHARED))
82 return MMAP_ALIGN_MASK << PAGE_SHIFT;
83 return 0;
84}
85
86unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
87 unsigned long len, unsigned long pgoff,
88 unsigned long flags, vm_flags_t vm_flags)
89{
90 struct mm_struct *mm = current->mm;
91 struct vm_area_struct *vma;
92 struct vm_unmapped_area_info info = {};
93
94 if (len > TASK_SIZE - mmap_min_addr)
95 return -ENOMEM;
96
97 if (flags & MAP_FIXED)
98 goto check_asce_limit;
99
100 if (addr) {
101 addr = PAGE_ALIGN(addr);
102 vma = find_vma(mm, addr);
103 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
104 (!vma || addr + len <= vm_start_gap(vma)))
105 goto check_asce_limit;
106 }
107
108 info.length = len;
109 info.low_limit = mm->mmap_base;
110 info.high_limit = TASK_SIZE;
111 info.align_mask = get_align_mask(filp, flags);
112 if (!(filp && is_file_hugepages(filp)))
113 info.align_offset = pgoff << PAGE_SHIFT;
114 addr = vm_unmapped_area(&info);
115 if (offset_in_page(addr))
116 return addr;
117
118check_asce_limit:
119 return check_asce_limit(mm, addr, len);
120}
121
122unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
123 unsigned long len, unsigned long pgoff,
124 unsigned long flags, vm_flags_t vm_flags)
125{
126 struct vm_area_struct *vma;
127 struct mm_struct *mm = current->mm;
128 struct vm_unmapped_area_info info = {};
129
130 /* requested length too big for entire address space */
131 if (len > TASK_SIZE - mmap_min_addr)
132 return -ENOMEM;
133
134 if (flags & MAP_FIXED)
135 goto check_asce_limit;
136
137 /* requesting a specific address */
138 if (addr) {
139 addr = PAGE_ALIGN(addr);
140 vma = find_vma(mm, addr);
141 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
142 (!vma || addr + len <= vm_start_gap(vma)))
143 goto check_asce_limit;
144 }
145
146 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
147 info.length = len;
148 info.low_limit = PAGE_SIZE;
149 info.high_limit = mm->mmap_base;
150 info.align_mask = get_align_mask(filp, flags);
151 if (!(filp && is_file_hugepages(filp)))
152 info.align_offset = pgoff << PAGE_SHIFT;
153 addr = vm_unmapped_area(&info);
154
155 /*
156 * A failed mmap() very likely causes application failure,
157 * so fall back to the bottom-up function here. This scenario
158 * can happen with large stack limits and large mmap()
159 * allocations.
160 */
161 if (offset_in_page(addr)) {
162 VM_BUG_ON(addr != -ENOMEM);
163 info.flags = 0;
164 info.low_limit = TASK_UNMAPPED_BASE;
165 info.high_limit = TASK_SIZE;
166 addr = vm_unmapped_area(&info);
167 if (offset_in_page(addr))
168 return addr;
169 }
170
171check_asce_limit:
172 return check_asce_limit(mm, addr, len);
173}
174
175/*
176 * This function, called very early during the creation of a new
177 * process VM image, sets up which VM layout function to use:
178 */
179void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
180{
181 unsigned long random_factor = 0UL;
182
183 if (current->flags & PF_RANDOMIZE)
184 random_factor = arch_mmap_rnd();
185
186 /*
187 * Fall back to the standard layout if the personality
188 * bit is set, or if the expected stack growth is unlimited:
189 */
190 if (mmap_is_legacy(rlim_stack)) {
191 mm->mmap_base = mmap_base_legacy(random_factor);
192 clear_bit(MMF_TOPDOWN, &mm->flags);
193 } else {
194 mm->mmap_base = mmap_base(random_factor, rlim_stack);
195 set_bit(MMF_TOPDOWN, &mm->flags);
196 }
197}
198
199static const pgprot_t protection_map[16] = {
200 [VM_NONE] = PAGE_NONE,
201 [VM_READ] = PAGE_RO,
202 [VM_WRITE] = PAGE_RO,
203 [VM_WRITE | VM_READ] = PAGE_RO,
204 [VM_EXEC] = PAGE_RX,
205 [VM_EXEC | VM_READ] = PAGE_RX,
206 [VM_EXEC | VM_WRITE] = PAGE_RX,
207 [VM_EXEC | VM_WRITE | VM_READ] = PAGE_RX,
208 [VM_SHARED] = PAGE_NONE,
209 [VM_SHARED | VM_READ] = PAGE_RO,
210 [VM_SHARED | VM_WRITE] = PAGE_RW,
211 [VM_SHARED | VM_WRITE | VM_READ] = PAGE_RW,
212 [VM_SHARED | VM_EXEC] = PAGE_RX,
213 [VM_SHARED | VM_EXEC | VM_READ] = PAGE_RX,
214 [VM_SHARED | VM_EXEC | VM_WRITE] = PAGE_RWX,
215 [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = PAGE_RWX
216};
217DECLARE_VM_GET_PAGE_PROT
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * flexible mmap layout support
4 *
5 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
6 * All Rights Reserved.
7 *
8 * Started by Ingo Molnar <mingo@elte.hu>
9 */
10
11#include <linux/elf-randomize.h>
12#include <linux/personality.h>
13#include <linux/mm.h>
14#include <linux/mman.h>
15#include <linux/sched/signal.h>
16#include <linux/sched/mm.h>
17#include <linux/random.h>
18#include <linux/compat.h>
19#include <linux/security.h>
20#include <asm/elf.h>
21
22static unsigned long stack_maxrandom_size(void)
23{
24 if (!(current->flags & PF_RANDOMIZE))
25 return 0;
26 return STACK_RND_MASK << PAGE_SHIFT;
27}
28
29static inline int mmap_is_legacy(struct rlimit *rlim_stack)
30{
31 if (current->personality & ADDR_COMPAT_LAYOUT)
32 return 1;
33 if (rlim_stack->rlim_cur == RLIM_INFINITY)
34 return 1;
35 return sysctl_legacy_va_layout;
36}
37
38unsigned long arch_mmap_rnd(void)
39{
40 return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
41}
42
43static unsigned long mmap_base_legacy(unsigned long rnd)
44{
45 return TASK_UNMAPPED_BASE + rnd;
46}
47
48static inline unsigned long mmap_base(unsigned long rnd,
49 struct rlimit *rlim_stack)
50{
51 unsigned long gap = rlim_stack->rlim_cur;
52 unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
53 unsigned long gap_min, gap_max;
54
55 /* Values close to RLIM_INFINITY can overflow. */
56 if (gap + pad > gap)
57 gap += pad;
58
59 /*
60 * Top of mmap area (just below the process stack).
61 * Leave at least a ~32 MB hole.
62 */
63 gap_min = 32 * 1024 * 1024UL;
64 gap_max = (STACK_TOP / 6) * 5;
65
66 if (gap < gap_min)
67 gap = gap_min;
68 else if (gap > gap_max)
69 gap = gap_max;
70
71 return PAGE_ALIGN(STACK_TOP - gap - rnd);
72}
73
74unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
75 unsigned long len, unsigned long pgoff,
76 unsigned long flags)
77{
78 struct mm_struct *mm = current->mm;
79 struct vm_area_struct *vma;
80 struct vm_unmapped_area_info info;
81
82 if (len > TASK_SIZE - mmap_min_addr)
83 return -ENOMEM;
84
85 if (flags & MAP_FIXED)
86 goto check_asce_limit;
87
88 if (addr) {
89 addr = PAGE_ALIGN(addr);
90 vma = find_vma(mm, addr);
91 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
92 (!vma || addr + len <= vm_start_gap(vma)))
93 goto check_asce_limit;
94 }
95
96 info.flags = 0;
97 info.length = len;
98 info.low_limit = mm->mmap_base;
99 info.high_limit = TASK_SIZE;
100 if (filp || (flags & MAP_SHARED))
101 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
102 else
103 info.align_mask = 0;
104 info.align_offset = pgoff << PAGE_SHIFT;
105 addr = vm_unmapped_area(&info);
106 if (offset_in_page(addr))
107 return addr;
108
109check_asce_limit:
110 return check_asce_limit(mm, addr, len);
111}
112
113unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
114 unsigned long len, unsigned long pgoff,
115 unsigned long flags)
116{
117 struct vm_area_struct *vma;
118 struct mm_struct *mm = current->mm;
119 struct vm_unmapped_area_info info;
120
121 /* requested length too big for entire address space */
122 if (len > TASK_SIZE - mmap_min_addr)
123 return -ENOMEM;
124
125 if (flags & MAP_FIXED)
126 goto check_asce_limit;
127
128 /* requesting a specific address */
129 if (addr) {
130 addr = PAGE_ALIGN(addr);
131 vma = find_vma(mm, addr);
132 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
133 (!vma || addr + len <= vm_start_gap(vma)))
134 goto check_asce_limit;
135 }
136
137 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
138 info.length = len;
139 info.low_limit = max(PAGE_SIZE, mmap_min_addr);
140 info.high_limit = mm->mmap_base;
141 if (filp || (flags & MAP_SHARED))
142 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
143 else
144 info.align_mask = 0;
145 info.align_offset = pgoff << PAGE_SHIFT;
146 addr = vm_unmapped_area(&info);
147
148 /*
149 * A failed mmap() very likely causes application failure,
150 * so fall back to the bottom-up function here. This scenario
151 * can happen with large stack limits and large mmap()
152 * allocations.
153 */
154 if (offset_in_page(addr)) {
155 VM_BUG_ON(addr != -ENOMEM);
156 info.flags = 0;
157 info.low_limit = TASK_UNMAPPED_BASE;
158 info.high_limit = TASK_SIZE;
159 addr = vm_unmapped_area(&info);
160 if (offset_in_page(addr))
161 return addr;
162 }
163
164check_asce_limit:
165 return check_asce_limit(mm, addr, len);
166}
167
168/*
169 * This function, called very early during the creation of a new
170 * process VM image, sets up which VM layout function to use:
171 */
172void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
173{
174 unsigned long random_factor = 0UL;
175
176 if (current->flags & PF_RANDOMIZE)
177 random_factor = arch_mmap_rnd();
178
179 /*
180 * Fall back to the standard layout if the personality
181 * bit is set, or if the expected stack growth is unlimited:
182 */
183 if (mmap_is_legacy(rlim_stack)) {
184 mm->mmap_base = mmap_base_legacy(random_factor);
185 mm->get_unmapped_area = arch_get_unmapped_area;
186 } else {
187 mm->mmap_base = mmap_base(random_factor, rlim_stack);
188 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
189 }
190}