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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Flexible mmap layout support
4 *
5 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
6 * as follows:
7 *
8 * Copyright 2003-2009 Red Hat Inc.
9 * All Rights Reserved.
10 * Copyright 2005 Andi Kleen, SUSE Labs.
11 * Copyright 2007 Jiri Kosina, SUSE Labs.
12 */
13
14#include <linux/personality.h>
15#include <linux/mm.h>
16#include <linux/random.h>
17#include <linux/limits.h>
18#include <linux/sched/signal.h>
19#include <linux/sched/mm.h>
20#include <linux/compat.h>
21#include <linux/elf-randomize.h>
22#include <asm/elf.h>
23#include <asm/io.h>
24
25#include "physaddr.h"
26
27struct va_alignment __read_mostly va_align = {
28 .flags = -1,
29};
30
31unsigned long task_size_32bit(void)
32{
33 return IA32_PAGE_OFFSET;
34}
35
36unsigned long task_size_64bit(int full_addr_space)
37{
38 return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
39}
40
41static unsigned long stack_maxrandom_size(unsigned long task_size)
42{
43 unsigned long max = 0;
44 if (current->flags & PF_RANDOMIZE) {
45 max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit());
46 max <<= PAGE_SHIFT;
47 }
48
49 return max;
50}
51
52#ifdef CONFIG_COMPAT
53# define mmap32_rnd_bits mmap_rnd_compat_bits
54# define mmap64_rnd_bits mmap_rnd_bits
55#else
56# define mmap32_rnd_bits mmap_rnd_bits
57# define mmap64_rnd_bits mmap_rnd_bits
58#endif
59
60#define SIZE_128M (128 * 1024 * 1024UL)
61
62static int mmap_is_legacy(void)
63{
64 if (current->personality & ADDR_COMPAT_LAYOUT)
65 return 1;
66
67 return sysctl_legacy_va_layout;
68}
69
70static unsigned long arch_rnd(unsigned int rndbits)
71{
72 if (!(current->flags & PF_RANDOMIZE))
73 return 0;
74 return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
75}
76
77unsigned long arch_mmap_rnd(void)
78{
79 return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
80}
81
82static unsigned long mmap_base(unsigned long rnd, unsigned long task_size,
83 struct rlimit *rlim_stack)
84{
85 unsigned long gap = rlim_stack->rlim_cur;
86 unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
87 unsigned long gap_min, gap_max;
88
89 /* Values close to RLIM_INFINITY can overflow. */
90 if (gap + pad > gap)
91 gap += pad;
92
93 /*
94 * Top of mmap area (just below the process stack).
95 * Leave an at least ~128 MB hole with possible stack randomization.
96 */
97 gap_min = SIZE_128M;
98 gap_max = (task_size / 6) * 5;
99
100 if (gap < gap_min)
101 gap = gap_min;
102 else if (gap > gap_max)
103 gap = gap_max;
104
105 return PAGE_ALIGN(task_size - gap - rnd);
106}
107
108static unsigned long mmap_legacy_base(unsigned long rnd,
109 unsigned long task_size)
110{
111 return __TASK_UNMAPPED_BASE(task_size) + rnd;
112}
113
114/*
115 * This function, called very early during the creation of a new
116 * process VM image, sets up which VM layout function to use:
117 */
118static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
119 unsigned long random_factor, unsigned long task_size,
120 struct rlimit *rlim_stack)
121{
122 *legacy_base = mmap_legacy_base(random_factor, task_size);
123 if (mmap_is_legacy())
124 *base = *legacy_base;
125 else
126 *base = mmap_base(random_factor, task_size, rlim_stack);
127}
128
129void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
130{
131 if (mmap_is_legacy())
132 mm->get_unmapped_area = arch_get_unmapped_area;
133 else
134 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
135
136 arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
137 arch_rnd(mmap64_rnd_bits), task_size_64bit(0),
138 rlim_stack);
139
140#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
141 /*
142 * The mmap syscall mapping base decision depends solely on the
143 * syscall type (64-bit or compat). This applies for 64bit
144 * applications and 32bit applications. The 64bit syscall uses
145 * mmap_base, the compat syscall uses mmap_compat_base.
146 */
147 arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
148 arch_rnd(mmap32_rnd_bits), task_size_32bit(),
149 rlim_stack);
150#endif
151}
152
153unsigned long get_mmap_base(int is_legacy)
154{
155 struct mm_struct *mm = current->mm;
156
157#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
158 if (in_32bit_syscall()) {
159 return is_legacy ? mm->mmap_compat_legacy_base
160 : mm->mmap_compat_base;
161 }
162#endif
163 return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
164}
165
166const char *arch_vma_name(struct vm_area_struct *vma)
167{
168 return NULL;
169}
170
171/**
172 * mmap_address_hint_valid - Validate the address hint of mmap
173 * @addr: Address hint
174 * @len: Mapping length
175 *
176 * Check whether @addr and @addr + @len result in a valid mapping.
177 *
178 * On 32bit this only checks whether @addr + @len is <= TASK_SIZE.
179 *
180 * On 64bit with 5-level page tables another sanity check is required
181 * because mappings requested by mmap(@addr, 0) which cross the 47-bit
182 * virtual address boundary can cause the following theoretical issue:
183 *
184 * An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr
185 * is below the border of the 47-bit address space and @addr + @len is
186 * above the border.
187 *
188 * With 4-level paging this request succeeds, but the resulting mapping
189 * address will always be within the 47-bit virtual address space, because
190 * the hint address does not result in a valid mapping and is
191 * ignored. Hence applications which are not prepared to handle virtual
192 * addresses above 47-bit work correctly.
193 *
194 * With 5-level paging this request would be granted and result in a
195 * mapping which crosses the border of the 47-bit virtual address
196 * space. If the application cannot handle addresses above 47-bit this
197 * will lead to misbehaviour and hard to diagnose failures.
198 *
199 * Therefore ignore address hints which would result in a mapping crossing
200 * the 47-bit virtual address boundary.
201 *
202 * Note, that in the same scenario with MAP_FIXED the behaviour is
203 * different. The request with @addr < 47-bit and @addr + @len > 47-bit
204 * fails on a 4-level paging machine but succeeds on a 5-level paging
205 * machine. It is reasonable to expect that an application does not rely on
206 * the failure of such a fixed mapping request, so the restriction is not
207 * applied.
208 */
209bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
210{
211 if (TASK_SIZE - len < addr)
212 return false;
213
214 return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW);
215}
216
217/* Can we access it for direct reading/writing? Must be RAM: */
218int valid_phys_addr_range(phys_addr_t addr, size_t count)
219{
220 return addr + count - 1 <= __pa(high_memory - 1);
221}
222
223/* Can we access it through mmap? Must be a valid physical address: */
224int valid_mmap_phys_addr_range(unsigned long pfn, size_t count)
225{
226 phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT;
227
228 return phys_addr_valid(addr + count - 1);
229}
230
231/*
232 * Only allow root to set high MMIO mappings to PROT_NONE.
233 * This prevents an unpriv. user to set them to PROT_NONE and invert
234 * them, then pointing to valid memory for L1TF speculation.
235 *
236 * Note: for locked down kernels may want to disable the root override.
237 */
238bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot)
239{
240 if (!boot_cpu_has_bug(X86_BUG_L1TF))
241 return true;
242 if (!__pte_needs_invert(pgprot_val(prot)))
243 return true;
244 /* If it's real memory always allow */
245 if (pfn_valid(pfn))
246 return true;
247 if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN))
248 return false;
249 return true;
250}
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Flexible mmap layout support
4 *
5 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
6 * as follows:
7 *
8 * Copyright 2003-2009 Red Hat Inc.
9 * All Rights Reserved.
10 * Copyright 2005 Andi Kleen, SUSE Labs.
11 * Copyright 2007 Jiri Kosina, SUSE Labs.
12 */
13
14#include <linux/personality.h>
15#include <linux/mm.h>
16#include <linux/random.h>
17#include <linux/limits.h>
18#include <linux/sched/signal.h>
19#include <linux/sched/mm.h>
20#include <linux/compat.h>
21#include <linux/elf-randomize.h>
22#include <asm/elf.h>
23#include <asm/io.h>
24
25#include "physaddr.h"
26
27struct va_alignment __read_mostly va_align = {
28 .flags = -1,
29};
30
31unsigned long task_size_32bit(void)
32{
33 return IA32_PAGE_OFFSET;
34}
35
36unsigned long task_size_64bit(int full_addr_space)
37{
38 return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
39}
40
41static unsigned long stack_maxrandom_size(unsigned long task_size)
42{
43 unsigned long max = 0;
44 if (current->flags & PF_RANDOMIZE) {
45 max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit());
46 max <<= PAGE_SHIFT;
47 }
48
49 return max;
50}
51
52#ifdef CONFIG_COMPAT
53# define mmap32_rnd_bits mmap_rnd_compat_bits
54# define mmap64_rnd_bits mmap_rnd_bits
55#else
56# define mmap32_rnd_bits mmap_rnd_bits
57# define mmap64_rnd_bits mmap_rnd_bits
58#endif
59
60#define SIZE_128M (128 * 1024 * 1024UL)
61
62static int mmap_is_legacy(void)
63{
64 if (current->personality & ADDR_COMPAT_LAYOUT)
65 return 1;
66
67 return sysctl_legacy_va_layout;
68}
69
70static unsigned long arch_rnd(unsigned int rndbits)
71{
72 if (!(current->flags & PF_RANDOMIZE))
73 return 0;
74 return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
75}
76
77unsigned long arch_mmap_rnd(void)
78{
79 return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
80}
81
82static unsigned long mmap_base(unsigned long rnd, unsigned long task_size,
83 struct rlimit *rlim_stack)
84{
85 unsigned long gap = rlim_stack->rlim_cur;
86 unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
87 unsigned long gap_min, gap_max;
88
89 /* Values close to RLIM_INFINITY can overflow. */
90 if (gap + pad > gap)
91 gap += pad;
92
93 /*
94 * Top of mmap area (just below the process stack).
95 * Leave an at least ~128 MB hole with possible stack randomization.
96 */
97 gap_min = SIZE_128M;
98 gap_max = (task_size / 6) * 5;
99
100 if (gap < gap_min)
101 gap = gap_min;
102 else if (gap > gap_max)
103 gap = gap_max;
104
105 return PAGE_ALIGN(task_size - gap - rnd);
106}
107
108static unsigned long mmap_legacy_base(unsigned long rnd,
109 unsigned long task_size)
110{
111 return __TASK_UNMAPPED_BASE(task_size) + rnd;
112}
113
114/*
115 * This function, called very early during the creation of a new
116 * process VM image, sets up which VM layout function to use:
117 */
118static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
119 unsigned long random_factor, unsigned long task_size,
120 struct rlimit *rlim_stack)
121{
122 *legacy_base = mmap_legacy_base(random_factor, task_size);
123 if (mmap_is_legacy())
124 *base = *legacy_base;
125 else
126 *base = mmap_base(random_factor, task_size, rlim_stack);
127}
128
129void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
130{
131 if (mmap_is_legacy())
132 clear_bit(MMF_TOPDOWN, &mm->flags);
133 else
134 set_bit(MMF_TOPDOWN, &mm->flags);
135
136 arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
137 arch_rnd(mmap64_rnd_bits), task_size_64bit(0),
138 rlim_stack);
139
140#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
141 /*
142 * The mmap syscall mapping base decision depends solely on the
143 * syscall type (64-bit or compat). This applies for 64bit
144 * applications and 32bit applications. The 64bit syscall uses
145 * mmap_base, the compat syscall uses mmap_compat_base.
146 */
147 arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
148 arch_rnd(mmap32_rnd_bits), task_size_32bit(),
149 rlim_stack);
150#endif
151}
152
153unsigned long get_mmap_base(int is_legacy)
154{
155 struct mm_struct *mm = current->mm;
156
157#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
158 if (in_32bit_syscall()) {
159 return is_legacy ? mm->mmap_compat_legacy_base
160 : mm->mmap_compat_base;
161 }
162#endif
163 return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
164}
165
166/**
167 * mmap_address_hint_valid - Validate the address hint of mmap
168 * @addr: Address hint
169 * @len: Mapping length
170 *
171 * Check whether @addr and @addr + @len result in a valid mapping.
172 *
173 * On 32bit this only checks whether @addr + @len is <= TASK_SIZE.
174 *
175 * On 64bit with 5-level page tables another sanity check is required
176 * because mappings requested by mmap(@addr, 0) which cross the 47-bit
177 * virtual address boundary can cause the following theoretical issue:
178 *
179 * An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr
180 * is below the border of the 47-bit address space and @addr + @len is
181 * above the border.
182 *
183 * With 4-level paging this request succeeds, but the resulting mapping
184 * address will always be within the 47-bit virtual address space, because
185 * the hint address does not result in a valid mapping and is
186 * ignored. Hence applications which are not prepared to handle virtual
187 * addresses above 47-bit work correctly.
188 *
189 * With 5-level paging this request would be granted and result in a
190 * mapping which crosses the border of the 47-bit virtual address
191 * space. If the application cannot handle addresses above 47-bit this
192 * will lead to misbehaviour and hard to diagnose failures.
193 *
194 * Therefore ignore address hints which would result in a mapping crossing
195 * the 47-bit virtual address boundary.
196 *
197 * Note, that in the same scenario with MAP_FIXED the behaviour is
198 * different. The request with @addr < 47-bit and @addr + @len > 47-bit
199 * fails on a 4-level paging machine but succeeds on a 5-level paging
200 * machine. It is reasonable to expect that an application does not rely on
201 * the failure of such a fixed mapping request, so the restriction is not
202 * applied.
203 */
204bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
205{
206 if (TASK_SIZE - len < addr)
207 return false;
208
209 return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW);
210}
211
212/* Can we access it for direct reading/writing? Must be RAM: */
213int valid_phys_addr_range(phys_addr_t addr, size_t count)
214{
215 return addr + count - 1 <= __pa(high_memory - 1);
216}
217
218/* Can we access it through mmap? Must be a valid physical address: */
219int valid_mmap_phys_addr_range(unsigned long pfn, size_t count)
220{
221 phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT;
222
223 return phys_addr_valid(addr + count - 1);
224}
225
226/*
227 * Only allow root to set high MMIO mappings to PROT_NONE.
228 * This prevents an unpriv. user to set them to PROT_NONE and invert
229 * them, then pointing to valid memory for L1TF speculation.
230 *
231 * Note: for locked down kernels may want to disable the root override.
232 */
233bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot)
234{
235 if (!boot_cpu_has_bug(X86_BUG_L1TF))
236 return true;
237 if (!__pte_needs_invert(pgprot_val(prot)))
238 return true;
239 /* If it's real memory always allow */
240 if (pfn_valid(pfn))
241 return true;
242 if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN))
243 return false;
244 return true;
245}