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