1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_UACCESS_H__
3#define __LINUX_UACCESS_H__
4
5#include <linux/fault-inject-usercopy.h>
6#include <linux/instrumented.h>
7#include <linux/minmax.h>
8#include <linux/sched.h>
9#include <linux/thread_info.h>
10
11#include <asm/uaccess.h>
12
13#ifdef CONFIG_SET_FS
14/*
15 * Force the uaccess routines to be wired up for actual userspace access,
16 * overriding any possible set_fs(KERNEL_DS) still lingering around.  Undone
17 * using force_uaccess_end below.
18 */
19static inline mm_segment_t force_uaccess_begin(void)
20{
21	mm_segment_t fs = get_fs();
22
23	set_fs(USER_DS);
24	return fs;
25}
26
27static inline void force_uaccess_end(mm_segment_t oldfs)
28{
29	set_fs(oldfs);
30}
31#else /* CONFIG_SET_FS */
32typedef struct {
33	/* empty dummy */
34} mm_segment_t;
35
36#ifndef TASK_SIZE_MAX
37#define TASK_SIZE_MAX			TASK_SIZE
38#endif
39
40#define uaccess_kernel()		(false)
41#define user_addr_max()			(TASK_SIZE_MAX)
42
43static inline mm_segment_t force_uaccess_begin(void)
44{
45	return (mm_segment_t) { };
46}
47
48static inline void force_uaccess_end(mm_segment_t oldfs)
49{
50}
51#endif /* CONFIG_SET_FS */
52
53/*
54 * Architectures should provide two primitives (raw_copy_{to,from}_user())
55 * and get rid of their private instances of copy_{to,from}_user() and
56 * __copy_{to,from}_user{,_inatomic}().
57 *
58 * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
59 * return the amount left to copy.  They should assume that access_ok() has
60 * already been checked (and succeeded); they should *not* zero-pad anything.
61 * No KASAN or object size checks either - those belong here.
62 *
63 * Both of these functions should attempt to copy size bytes starting at from
64 * into the area starting at to.  They must not fetch or store anything
65 * outside of those areas.  Return value must be between 0 (everything
66 * copied successfully) and size (nothing copied).
67 *
68 * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
69 * at to must become equal to the bytes fetched from the corresponding area
70 * starting at from.  All data past to + size - N must be left unmodified.
71 *
72 * If copying succeeds, the return value must be 0.  If some data cannot be
73 * fetched, it is permitted to copy less than had been fetched; the only
74 * hard requirement is that not storing anything at all (i.e. returning size)
75 * should happen only when nothing could be copied.  In other words, you don't
76 * have to squeeze as much as possible - it is allowed, but not necessary.
77 *
78 * For raw_copy_from_user() to always points to kernel memory and no faults
79 * on store should happen.  Interpretation of from is affected by set_fs().
80 * For raw_copy_to_user() it's the other way round.
81 *
82 * Both can be inlined - it's up to architectures whether it wants to bother
83 * with that.  They should not be used directly; they are used to implement
84 * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
85 * that are used instead.  Out of those, __... ones are inlined.  Plain
86 * copy_{to,from}_user() might or might not be inlined.  If you want them
87 * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
88 *
89 * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
90 * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
91 * at all; their callers absolutely must check the return value.
92 *
93 * Biarch ones should also provide raw_copy_in_user() - similar to the above,
94 * but both source and destination are __user pointers (affected by set_fs()
95 * as usual) and both source and destination can trigger faults.
96 */
97
98static __always_inline __must_check unsigned long
99__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
100{
101	instrument_copy_from_user(to, from, n);
102	check_object_size(to, n, false);
103	return raw_copy_from_user(to, from, n);
104}
105
106static __always_inline __must_check unsigned long
107__copy_from_user(void *to, const void __user *from, unsigned long n)
108{
109	might_fault();
110	if (should_fail_usercopy())
111		return n;
112	instrument_copy_from_user(to, from, n);
113	check_object_size(to, n, false);
114	return raw_copy_from_user(to, from, n);
115}
116
117/**
118 * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
119 * @to:   Destination address, in user space.
120 * @from: Source address, in kernel space.
121 * @n:    Number of bytes to copy.
122 *
123 * Context: User context only.
124 *
125 * Copy data from kernel space to user space.  Caller must check
126 * the specified block with access_ok() before calling this function.
127 * The caller should also make sure he pins the user space address
128 * so that we don't result in page fault and sleep.
129 */
130static __always_inline __must_check unsigned long
131__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
132{
133	if (should_fail_usercopy())
134		return n;
135	instrument_copy_to_user(to, from, n);
136	check_object_size(from, n, true);
137	return raw_copy_to_user(to, from, n);
138}
139
140static __always_inline __must_check unsigned long
141__copy_to_user(void __user *to, const void *from, unsigned long n)
142{
143	might_fault();
144	if (should_fail_usercopy())
145		return n;
146	instrument_copy_to_user(to, from, n);
147	check_object_size(from, n, true);
148	return raw_copy_to_user(to, from, n);
149}
150
151#ifdef INLINE_COPY_FROM_USER
152static inline __must_check unsigned long
153_copy_from_user(void *to, const void __user *from, unsigned long n)
154{
155	unsigned long res = n;
156	might_fault();
157	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
158		instrument_copy_from_user(to, from, n);
159		res = raw_copy_from_user(to, from, n);
160	}
161	if (unlikely(res))
162		memset(to + (n - res), 0, res);
163	return res;
164}
165#else
166extern __must_check unsigned long
167_copy_from_user(void *, const void __user *, unsigned long);
168#endif
169
170#ifdef INLINE_COPY_TO_USER
171static inline __must_check unsigned long
172_copy_to_user(void __user *to, const void *from, unsigned long n)
173{
174	might_fault();
175	if (should_fail_usercopy())
176		return n;
177	if (access_ok(to, n)) {
178		instrument_copy_to_user(to, from, n);
179		n = raw_copy_to_user(to, from, n);
180	}
181	return n;
182}
183#else
184extern __must_check unsigned long
185_copy_to_user(void __user *, const void *, unsigned long);
186#endif
187
188static __always_inline unsigned long __must_check
189copy_from_user(void *to, const void __user *from, unsigned long n)
190{
191	if (likely(check_copy_size(to, n, false)))
192		n = _copy_from_user(to, from, n);
193	return n;
194}
195
196static __always_inline unsigned long __must_check
197copy_to_user(void __user *to, const void *from, unsigned long n)
198{
199	if (likely(check_copy_size(from, n, true)))
200		n = _copy_to_user(to, from, n);
201	return n;
202}
203
204#ifndef copy_mc_to_kernel
205/*
206 * Without arch opt-in this generic copy_mc_to_kernel() will not handle
207 * #MC (or arch equivalent) during source read.
208 */
209static inline unsigned long __must_check
210copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
211{
212	memcpy(dst, src, cnt);
213	return 0;
214}
215#endif
216
217static __always_inline void pagefault_disabled_inc(void)
218{
219	current->pagefault_disabled++;
220}
221
222static __always_inline void pagefault_disabled_dec(void)
223{
224	current->pagefault_disabled--;
225}
226
227/*
228 * These routines enable/disable the pagefault handler. If disabled, it will
229 * not take any locks and go straight to the fixup table.
230 *
231 * User access methods will not sleep when called from a pagefault_disabled()
232 * environment.
233 */
234static inline void pagefault_disable(void)
235{
236	pagefault_disabled_inc();
237	/*
238	 * make sure to have issued the store before a pagefault
239	 * can hit.
240	 */
241	barrier();
242}
243
244static inline void pagefault_enable(void)
245{
246	/*
247	 * make sure to issue those last loads/stores before enabling
248	 * the pagefault handler again.
249	 */
250	barrier();
251	pagefault_disabled_dec();
252}
253
254/*
255 * Is the pagefault handler disabled? If so, user access methods will not sleep.
256 */
257static inline bool pagefault_disabled(void)
258{
259	return current->pagefault_disabled != 0;
260}
261
262/*
263 * The pagefault handler is in general disabled by pagefault_disable() or
264 * when in irq context (via in_atomic()).
265 *
266 * This function should only be used by the fault handlers. Other users should
267 * stick to pagefault_disabled().
268 * Please NEVER use preempt_disable() to disable the fault handler. With
269 * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
270 * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
271 */
272#define faulthandler_disabled() (pagefault_disabled() || in_atomic())
273
274#ifndef ARCH_HAS_NOCACHE_UACCESS
275
276static inline __must_check unsigned long
277__copy_from_user_inatomic_nocache(void *to, const void __user *from,
278				  unsigned long n)
279{
280	return __copy_from_user_inatomic(to, from, n);
281}
282
283#endif		/* ARCH_HAS_NOCACHE_UACCESS */
284
285extern __must_check int check_zeroed_user(const void __user *from, size_t size);
286
287/**
288 * copy_struct_from_user: copy a struct from userspace
289 * @dst:   Destination address, in kernel space. This buffer must be @ksize
290 *         bytes long.
291 * @ksize: Size of @dst struct.
292 * @src:   Source address, in userspace.
293 * @usize: (Alleged) size of @src struct.
294 *
295 * Copies a struct from userspace to kernel space, in a way that guarantees
296 * backwards-compatibility for struct syscall arguments (as long as future
297 * struct extensions are made such that all new fields are *appended* to the
298 * old struct, and zeroed-out new fields have the same meaning as the old
299 * struct).
300 *
301 * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
302 * The recommended usage is something like the following:
303 *
304 *   SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
305 *   {
306 *      int err;
307 *      struct foo karg = {};
308 *
309 *      if (usize > PAGE_SIZE)
310 *        return -E2BIG;
311 *      if (usize < FOO_SIZE_VER0)
312 *        return -EINVAL;
313 *
314 *      err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
315 *      if (err)
316 *        return err;
317 *
318 *      // ...
319 *   }
320 *
321 * There are three cases to consider:
322 *  * If @usize == @ksize, then it's copied verbatim.
323 *  * If @usize < @ksize, then the userspace has passed an old struct to a
324 *    newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
325 *    are to be zero-filled.
326 *  * If @usize > @ksize, then the userspace has passed a new struct to an
327 *    older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
328 *    are checked to ensure they are zeroed, otherwise -E2BIG is returned.
329 *
330 * Returns (in all cases, some data may have been copied):
331 *  * -E2BIG:  (@usize > @ksize) and there are non-zero trailing bytes in @src.
332 *  * -EFAULT: access to userspace failed.
333 */
334static __always_inline __must_check int
335copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
336		      size_t usize)
337{
338	size_t size = min(ksize, usize);
339	size_t rest = max(ksize, usize) - size;
340
341	/* Deal with trailing bytes. */
342	if (usize < ksize) {
343		memset(dst + size, 0, rest);
344	} else if (usize > ksize) {
345		int ret = check_zeroed_user(src + size, rest);
346		if (ret <= 0)
347			return ret ?: -E2BIG;
348	}
349	/* Copy the interoperable parts of the struct. */
350	if (copy_from_user(dst, src, size))
351		return -EFAULT;
352	return 0;
353}
354
355bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
356
357long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
358long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
359
360long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
361long notrace copy_to_user_nofault(void __user *dst, const void *src,
362		size_t size);
363
364long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
365		long count);
366
367long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
368		long count);
369long strnlen_user_nofault(const void __user *unsafe_addr, long count);
370
371/**
372 * get_kernel_nofault(): safely attempt to read from a location
373 * @val: read into this variable
374 * @ptr: address to read from
375 *
376 * Returns 0 on success, or -EFAULT.
377 */
378#define get_kernel_nofault(val, ptr) ({				\
379	const typeof(val) *__gk_ptr = (ptr);			\
380	copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
381})
382
383#ifndef user_access_begin
384#define user_access_begin(ptr,len) access_ok(ptr, len)
385#define user_access_end() do { } while (0)
386#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
387#define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
388#define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
389#define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
390#define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e)
391static inline unsigned long user_access_save(void) { return 0UL; }
392static inline void user_access_restore(unsigned long flags) { }
393#endif
394#ifndef user_write_access_begin
395#define user_write_access_begin user_access_begin
396#define user_write_access_end user_access_end
397#endif
398#ifndef user_read_access_begin
399#define user_read_access_begin user_access_begin
400#define user_read_access_end user_access_end
401#endif
402
403#ifdef CONFIG_HARDENED_USERCOPY
404void usercopy_warn(const char *name, const char *detail, bool to_user,
405		   unsigned long offset, unsigned long len);
406void __noreturn usercopy_abort(const char *name, const char *detail,
407			       bool to_user, unsigned long offset,
408			       unsigned long len);
409#endif
410
411#endif		/* __LINUX_UACCESS_H__ */
412