]>
Commit | Line | Data |
---|---|---|
cc503c1b | 1 | /* |
675a0813 | 2 | * Flexible mmap layout support |
cc503c1b JK |
3 | * |
4 | * Based on code by Ingo Molnar and Andi Kleen, copyrighted | |
5 | * as follows: | |
6 | * | |
8f47e163 | 7 | * Copyright 2003-2009 Red Hat Inc. |
cc503c1b JK |
8 | * All Rights Reserved. |
9 | * Copyright 2005 Andi Kleen, SUSE Labs. | |
10 | * Copyright 2007 Jiri Kosina, SUSE Labs. | |
11 | * | |
12 | * This program is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU General Public License as published by | |
14 | * the Free Software Foundation; either version 2 of the License, or | |
15 | * (at your option) any later version. | |
16 | * | |
17 | * This program is distributed in the hope that it will be useful, | |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU General Public License for more details. | |
21 | * | |
22 | * You should have received a copy of the GNU General Public License | |
23 | * along with this program; if not, write to the Free Software | |
24 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
8817210d | 25 | */ |
cc503c1b JK |
26 | |
27 | #include <linux/personality.h> | |
8817210d | 28 | #include <linux/mm.h> |
8817210d | 29 | #include <linux/random.h> |
cc503c1b | 30 | #include <linux/limits.h> |
3f07c014 | 31 | #include <linux/sched/signal.h> |
01042607 | 32 | #include <linux/sched/mm.h> |
e13b73dd | 33 | #include <linux/compat.h> |
80938332 MH |
34 | #include <asm/elf.h> |
35 | ||
be62a320 CB |
36 | #include "physaddr.h" |
37 | ||
cc99535e | 38 | struct va_alignment __read_mostly va_align = { |
9387f774 BP |
39 | .flags = -1, |
40 | }; | |
41 | ||
e8f01a8d | 42 | unsigned long task_size_32bit(void) |
8f3e474f DS |
43 | { |
44 | return IA32_PAGE_OFFSET; | |
45 | } | |
46 | ||
b569bab7 | 47 | unsigned long task_size_64bit(int full_addr_space) |
1b028f78 | 48 | { |
b569bab7 | 49 | return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW; |
1b028f78 DS |
50 | } |
51 | ||
8f3e474f | 52 | static unsigned long stack_maxrandom_size(unsigned long task_size) |
80938332 | 53 | { |
4e7c22d4 | 54 | unsigned long max = 0; |
01578e36 | 55 | if (current->flags & PF_RANDOMIZE) { |
e8f01a8d | 56 | max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit()); |
8f3e474f | 57 | max <<= PAGE_SHIFT; |
80938332 MH |
58 | } |
59 | ||
60 | return max; | |
61 | } | |
62 | ||
6a0b41d1 DS |
63 | #ifdef CONFIG_COMPAT |
64 | # define mmap32_rnd_bits mmap_rnd_compat_bits | |
65 | # define mmap64_rnd_bits mmap_rnd_bits | |
66 | #else | |
67 | # define mmap32_rnd_bits mmap_rnd_bits | |
68 | # define mmap64_rnd_bits mmap_rnd_bits | |
69 | #endif | |
70 | ||
8f3e474f DS |
71 | #define SIZE_128M (128 * 1024 * 1024UL) |
72 | ||
954683a2 | 73 | static int mmap_is_legacy(void) |
cc503c1b JK |
74 | { |
75 | if (current->personality & ADDR_COMPAT_LAYOUT) | |
76 | return 1; | |
77 | ||
cc503c1b JK |
78 | return sysctl_legacy_va_layout; |
79 | } | |
80 | ||
6a0b41d1 | 81 | static unsigned long arch_rnd(unsigned int rndbits) |
675a0813 | 82 | { |
47ac5484 ON |
83 | if (!(current->flags & PF_RANDOMIZE)) |
84 | return 0; | |
6a0b41d1 DS |
85 | return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT; |
86 | } | |
82168140 | 87 | |
6a0b41d1 DS |
88 | unsigned long arch_mmap_rnd(void) |
89 | { | |
90 | return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits); | |
675a0813 HH |
91 | } |
92 | ||
8f3e474f | 93 | static unsigned long mmap_base(unsigned long rnd, unsigned long task_size) |
675a0813 | 94 | { |
2854e72b | 95 | unsigned long gap = rlimit(RLIMIT_STACK); |
c204d21f | 96 | unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap; |
8f3e474f DS |
97 | unsigned long gap_min, gap_max; |
98 | ||
c204d21f RR |
99 | /* Values close to RLIM_INFINITY can overflow. */ |
100 | if (gap + pad > gap) | |
101 | gap += pad; | |
102 | ||
8f3e474f DS |
103 | /* |
104 | * Top of mmap area (just below the process stack). | |
105 | * Leave an at least ~128 MB hole with possible stack randomization. | |
106 | */ | |
c204d21f | 107 | gap_min = SIZE_128M; |
8f3e474f | 108 | gap_max = (task_size / 6) * 5; |
675a0813 | 109 | |
8f3e474f DS |
110 | if (gap < gap_min) |
111 | gap = gap_min; | |
112 | else if (gap > gap_max) | |
113 | gap = gap_max; | |
675a0813 | 114 | |
8f3e474f DS |
115 | return PAGE_ALIGN(task_size - gap - rnd); |
116 | } | |
117 | ||
118 | static unsigned long mmap_legacy_base(unsigned long rnd, | |
119 | unsigned long task_size) | |
120 | { | |
121 | return __TASK_UNMAPPED_BASE(task_size) + rnd; | |
675a0813 HH |
122 | } |
123 | ||
cc503c1b JK |
124 | /* |
125 | * This function, called very early during the creation of a new | |
126 | * process VM image, sets up which VM layout function to use: | |
127 | */ | |
1b028f78 DS |
128 | static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base, |
129 | unsigned long random_factor, unsigned long task_size) | |
cc503c1b | 130 | { |
1b028f78 DS |
131 | *legacy_base = mmap_legacy_base(random_factor, task_size); |
132 | if (mmap_is_legacy()) | |
133 | *base = *legacy_base; | |
134 | else | |
135 | *base = mmap_base(random_factor, task_size); | |
136 | } | |
41aacc1e | 137 | |
1b028f78 DS |
138 | void arch_pick_mmap_layout(struct mm_struct *mm) |
139 | { | |
140 | if (mmap_is_legacy()) | |
cc503c1b | 141 | mm->get_unmapped_area = arch_get_unmapped_area; |
1b028f78 | 142 | else |
cc503c1b | 143 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
1b028f78 DS |
144 | |
145 | arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base, | |
b569bab7 | 146 | arch_rnd(mmap64_rnd_bits), task_size_64bit(0)); |
1b028f78 DS |
147 | |
148 | #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES | |
149 | /* | |
150 | * The mmap syscall mapping base decision depends solely on the | |
151 | * syscall type (64-bit or compat). This applies for 64bit | |
152 | * applications and 32bit applications. The 64bit syscall uses | |
153 | * mmap_base, the compat syscall uses mmap_compat_base. | |
154 | */ | |
155 | arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base, | |
e8f01a8d | 156 | arch_rnd(mmap32_rnd_bits), task_size_32bit()); |
1b028f78 | 157 | #endif |
8817210d | 158 | } |
a8965276 | 159 | |
e13b73dd DS |
160 | unsigned long get_mmap_base(int is_legacy) |
161 | { | |
162 | struct mm_struct *mm = current->mm; | |
163 | ||
164 | #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES | |
165 | if (in_compat_syscall()) { | |
166 | return is_legacy ? mm->mmap_compat_legacy_base | |
167 | : mm->mmap_compat_base; | |
168 | } | |
169 | #endif | |
170 | return is_legacy ? mm->mmap_legacy_base : mm->mmap_base; | |
171 | } | |
172 | ||
a8965276 KS |
173 | const char *arch_vma_name(struct vm_area_struct *vma) |
174 | { | |
175 | if (vma->vm_flags & VM_MPX) | |
176 | return "[mpx]"; | |
177 | return NULL; | |
178 | } | |
1e0f25db KS |
179 | |
180 | /** | |
181 | * mmap_address_hint_valid - Validate the address hint of mmap | |
182 | * @addr: Address hint | |
183 | * @len: Mapping length | |
184 | * | |
185 | * Check whether @addr and @addr + @len result in a valid mapping. | |
186 | * | |
187 | * On 32bit this only checks whether @addr + @len is <= TASK_SIZE. | |
188 | * | |
189 | * On 64bit with 5-level page tables another sanity check is required | |
190 | * because mappings requested by mmap(@addr, 0) which cross the 47-bit | |
191 | * virtual address boundary can cause the following theoretical issue: | |
192 | * | |
193 | * An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr | |
194 | * is below the border of the 47-bit address space and @addr + @len is | |
195 | * above the border. | |
196 | * | |
197 | * With 4-level paging this request succeeds, but the resulting mapping | |
198 | * address will always be within the 47-bit virtual address space, because | |
199 | * the hint address does not result in a valid mapping and is | |
200 | * ignored. Hence applications which are not prepared to handle virtual | |
201 | * addresses above 47-bit work correctly. | |
202 | * | |
203 | * With 5-level paging this request would be granted and result in a | |
204 | * mapping which crosses the border of the 47-bit virtual address | |
205 | * space. If the application cannot handle addresses above 47-bit this | |
206 | * will lead to misbehaviour and hard to diagnose failures. | |
207 | * | |
208 | * Therefore ignore address hints which would result in a mapping crossing | |
209 | * the 47-bit virtual address boundary. | |
210 | * | |
211 | * Note, that in the same scenario with MAP_FIXED the behaviour is | |
212 | * different. The request with @addr < 47-bit and @addr + @len > 47-bit | |
213 | * fails on a 4-level paging machine but succeeds on a 5-level paging | |
214 | * machine. It is reasonable to expect that an application does not rely on | |
215 | * the failure of such a fixed mapping request, so the restriction is not | |
216 | * applied. | |
217 | */ | |
218 | bool mmap_address_hint_valid(unsigned long addr, unsigned long len) | |
219 | { | |
220 | if (TASK_SIZE - len < addr) | |
221 | return false; | |
222 | ||
223 | return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW); | |
224 | } | |
be62a320 CB |
225 | |
226 | /* Can we access it for direct reading/writing? Must be RAM: */ | |
227 | int valid_phys_addr_range(phys_addr_t addr, size_t count) | |
228 | { | |
03f43920 | 229 | return addr + count - 1 <= __pa(high_memory - 1); |
be62a320 CB |
230 | } |
231 | ||
232 | /* Can we access it through mmap? Must be a valid physical address: */ | |
233 | int valid_mmap_phys_addr_range(unsigned long pfn, size_t count) | |
234 | { | |
235 | phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT; | |
236 | ||
237 | return phys_addr_valid(addr + count - 1); | |
238 | } | |
0831b2a2 AK |
239 | |
240 | /* | |
241 | * Only allow root to set high MMIO mappings to PROT_NONE. | |
242 | * This prevents an unpriv. user to set them to PROT_NONE and invert | |
243 | * them, then pointing to valid memory for L1TF speculation. | |
244 | * | |
245 | * Note: for locked down kernels may want to disable the root override. | |
246 | */ | |
247 | bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot) | |
248 | { | |
249 | if (!boot_cpu_has_bug(X86_BUG_L1TF)) | |
250 | return true; | |
251 | if (!__pte_needs_invert(pgprot_val(prot))) | |
252 | return true; | |
253 | /* If it's real memory always allow */ | |
254 | if (pfn_valid(pfn)) | |
255 | return true; | |
c8ed7365 | 256 | if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN)) |
0831b2a2 AK |
257 | return false; |
258 | return true; | |
259 | } |