vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems
[linux/fpc-iii.git] / mm / usercopy.c
bloba9852b24715d25598a7603560ffc042ca0153a2b
1 /*
2 * This implements the various checks for CONFIG_HARDENED_USERCOPY*,
3 * which are designed to protect kernel memory from needless exposure
4 * and overwrite under many unintended conditions. This code is based
5 * on PAX_USERCOPY, which is:
7 * Copyright (C) 2001-2016 PaX Team, Bradley Spengler, Open Source
8 * Security Inc.
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License version 2 as
12 * published by the Free Software Foundation.
15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 #include <linux/mm.h>
18 #include <linux/slab.h>
19 #include <linux/sched.h>
20 #include <linux/sched/task.h>
21 #include <linux/sched/task_stack.h>
22 #include <linux/thread_info.h>
23 #include <asm/sections.h>
26 * Checks if a given pointer and length is contained by the current
27 * stack frame (if possible).
29 * Returns:
30 * NOT_STACK: not at all on the stack
31 * GOOD_FRAME: fully within a valid stack frame
32 * GOOD_STACK: fully on the stack (when can't do frame-checking)
33 * BAD_STACK: error condition (invalid stack position or bad stack frame)
35 static noinline int check_stack_object(const void *obj, unsigned long len)
37 const void * const stack = task_stack_page(current);
38 const void * const stackend = stack + THREAD_SIZE;
39 int ret;
41 /* Object is not on the stack at all. */
42 if (obj + len <= stack || stackend <= obj)
43 return NOT_STACK;
46 * Reject: object partially overlaps the stack (passing the
47 * the check above means at least one end is within the stack,
48 * so if this check fails, the other end is outside the stack).
50 if (obj < stack || stackend < obj + len)
51 return BAD_STACK;
53 /* Check if object is safely within a valid frame. */
54 ret = arch_within_stack_frames(stack, stackend, obj, len);
55 if (ret)
56 return ret;
58 return GOOD_STACK;
61 static void report_usercopy(const void *ptr, unsigned long len,
62 bool to_user, const char *type)
64 pr_emerg("kernel memory %s attempt detected %s %p (%s) (%lu bytes)\n",
65 to_user ? "exposure" : "overwrite",
66 to_user ? "from" : "to", ptr, type ? : "unknown", len);
68 * For greater effect, it would be nice to do do_group_exit(),
69 * but BUG() actually hooks all the lock-breaking and per-arch
70 * Oops code, so that is used here instead.
72 BUG();
75 /* Returns true if any portion of [ptr,ptr+n) over laps with [low,high). */
76 static bool overlaps(const void *ptr, unsigned long n, unsigned long low,
77 unsigned long high)
79 unsigned long check_low = (uintptr_t)ptr;
80 unsigned long check_high = check_low + n;
82 /* Does not overlap if entirely above or entirely below. */
83 if (check_low >= high || check_high <= low)
84 return false;
86 return true;
89 /* Is this address range in the kernel text area? */
90 static inline const char *check_kernel_text_object(const void *ptr,
91 unsigned long n)
93 unsigned long textlow = (unsigned long)_stext;
94 unsigned long texthigh = (unsigned long)_etext;
95 unsigned long textlow_linear, texthigh_linear;
97 if (overlaps(ptr, n, textlow, texthigh))
98 return "<kernel text>";
101 * Some architectures have virtual memory mappings with a secondary
102 * mapping of the kernel text, i.e. there is more than one virtual
103 * kernel address that points to the kernel image. It is usually
104 * when there is a separate linear physical memory mapping, in that
105 * __pa() is not just the reverse of __va(). This can be detected
106 * and checked:
108 textlow_linear = (unsigned long)lm_alias(textlow);
109 /* No different mapping: we're done. */
110 if (textlow_linear == textlow)
111 return NULL;
113 /* Check the secondary mapping... */
114 texthigh_linear = (unsigned long)lm_alias(texthigh);
115 if (overlaps(ptr, n, textlow_linear, texthigh_linear))
116 return "<linear kernel text>";
118 return NULL;
121 static inline const char *check_bogus_address(const void *ptr, unsigned long n)
123 /* Reject if object wraps past end of memory. */
124 if ((unsigned long)ptr + n < (unsigned long)ptr)
125 return "<wrapped address>";
127 /* Reject if NULL or ZERO-allocation. */
128 if (ZERO_OR_NULL_PTR(ptr))
129 return "<null>";
131 return NULL;
134 /* Checks for allocs that are marked in some way as spanning multiple pages. */
135 static inline const char *check_page_span(const void *ptr, unsigned long n,
136 struct page *page, bool to_user)
138 #ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN
139 const void *end = ptr + n - 1;
140 struct page *endpage;
141 bool is_reserved, is_cma;
144 * Sometimes the kernel data regions are not marked Reserved (see
145 * check below). And sometimes [_sdata,_edata) does not cover
146 * rodata and/or bss, so check each range explicitly.
149 /* Allow reads of kernel rodata region (if not marked as Reserved). */
150 if (ptr >= (const void *)__start_rodata &&
151 end <= (const void *)__end_rodata) {
152 if (!to_user)
153 return "<rodata>";
154 return NULL;
157 /* Allow kernel data region (if not marked as Reserved). */
158 if (ptr >= (const void *)_sdata && end <= (const void *)_edata)
159 return NULL;
161 /* Allow kernel bss region (if not marked as Reserved). */
162 if (ptr >= (const void *)__bss_start &&
163 end <= (const void *)__bss_stop)
164 return NULL;
166 /* Is the object wholly within one base page? */
167 if (likely(((unsigned long)ptr & (unsigned long)PAGE_MASK) ==
168 ((unsigned long)end & (unsigned long)PAGE_MASK)))
169 return NULL;
171 /* Allow if fully inside the same compound (__GFP_COMP) page. */
172 endpage = virt_to_head_page(end);
173 if (likely(endpage == page))
174 return NULL;
177 * Reject if range is entirely either Reserved (i.e. special or
178 * device memory), or CMA. Otherwise, reject since the object spans
179 * several independently allocated pages.
181 is_reserved = PageReserved(page);
182 is_cma = is_migrate_cma_page(page);
183 if (!is_reserved && !is_cma)
184 return "<spans multiple pages>";
186 for (ptr += PAGE_SIZE; ptr <= end; ptr += PAGE_SIZE) {
187 page = virt_to_head_page(ptr);
188 if (is_reserved && !PageReserved(page))
189 return "<spans Reserved and non-Reserved pages>";
190 if (is_cma && !is_migrate_cma_page(page))
191 return "<spans CMA and non-CMA pages>";
193 #endif
195 return NULL;
198 static inline const char *check_heap_object(const void *ptr, unsigned long n,
199 bool to_user)
201 struct page *page;
203 if (!virt_addr_valid(ptr))
204 return NULL;
206 page = virt_to_head_page(ptr);
208 /* Check slab allocator for flags and size. */
209 if (PageSlab(page))
210 return __check_heap_object(ptr, n, page);
212 /* Verify object does not incorrectly span multiple pages. */
213 return check_page_span(ptr, n, page, to_user);
217 * Validates that the given object is:
218 * - not bogus address
219 * - known-safe heap or stack object
220 * - not in kernel text
222 void __check_object_size(const void *ptr, unsigned long n, bool to_user)
224 const char *err;
226 /* Skip all tests if size is zero. */
227 if (!n)
228 return;
230 /* Check for invalid addresses. */
231 err = check_bogus_address(ptr, n);
232 if (err)
233 goto report;
235 /* Check for bad heap object. */
236 err = check_heap_object(ptr, n, to_user);
237 if (err)
238 goto report;
240 /* Check for bad stack object. */
241 switch (check_stack_object(ptr, n)) {
242 case NOT_STACK:
243 /* Object is not touching the current process stack. */
244 break;
245 case GOOD_FRAME:
246 case GOOD_STACK:
248 * Object is either in the correct frame (when it
249 * is possible to check) or just generally on the
250 * process stack (when frame checking not available).
252 return;
253 default:
254 err = "<process stack>";
255 goto report;
258 /* Check for object in kernel to avoid text exposure. */
259 err = check_kernel_text_object(ptr, n);
260 if (!err)
261 return;
263 report:
264 report_usercopy(ptr, n, to_user, err);
266 EXPORT_SYMBOL(__check_object_size);