1 #include <linux/mm.h> 2 #include <linux/slab.h> 3 #include <linux/string.h> 4 #include <linux/compiler.h> 5 #include <linux/export.h> 6 #include <linux/err.h> 7 #include <linux/sched.h> 8 #include <linux/security.h> 9 #include <linux/swap.h> 10 #include <linux/swapops.h> 11 #include <linux/mman.h> 12 #include <linux/hugetlb.h> 13 #include <linux/vmalloc.h> 14 15 #include <asm/sections.h> 16 #include <asm/uaccess.h> 17 18 #include "internal.h" 19 20 static inline int is_kernel_rodata(unsigned long addr) 21 { 22 return addr >= (unsigned long)__start_rodata && 23 addr < (unsigned long)__end_rodata; 24 } 25 26 /** 27 * kfree_const - conditionally free memory 28 * @x: pointer to the memory 29 * 30 * Function calls kfree only if @x is not in .rodata section. 31 */ 32 void kfree_const(const void *x) 33 { 34 if (!is_kernel_rodata((unsigned long)x)) 35 kfree(x); 36 } 37 EXPORT_SYMBOL(kfree_const); 38 39 /** 40 * kstrdup - allocate space for and copy an existing string 41 * @s: the string to duplicate 42 * @gfp: the GFP mask used in the kmalloc() call when allocating memory 43 */ 44 char *kstrdup(const char *s, gfp_t gfp) 45 { 46 size_t len; 47 char *buf; 48 49 if (!s) 50 return NULL; 51 52 len = strlen(s) + 1; 53 buf = kmalloc_track_caller(len, gfp); 54 if (buf) 55 memcpy(buf, s, len); 56 return buf; 57 } 58 EXPORT_SYMBOL(kstrdup); 59 60 /** 61 * kstrdup_const - conditionally duplicate an existing const string 62 * @s: the string to duplicate 63 * @gfp: the GFP mask used in the kmalloc() call when allocating memory 64 * 65 * Function returns source string if it is in .rodata section otherwise it 66 * fallbacks to kstrdup. 67 * Strings allocated by kstrdup_const should be freed by kfree_const. 68 */ 69 const char *kstrdup_const(const char *s, gfp_t gfp) 70 { 71 if (is_kernel_rodata((unsigned long)s)) 72 return s; 73 74 return kstrdup(s, gfp); 75 } 76 EXPORT_SYMBOL(kstrdup_const); 77 78 /** 79 * kstrndup - allocate space for and copy an existing string 80 * @s: the string to duplicate 81 * @max: read at most @max chars from @s 82 * @gfp: the GFP mask used in the kmalloc() call when allocating memory 83 */ 84 char *kstrndup(const char *s, size_t max, gfp_t gfp) 85 { 86 size_t len; 87 char *buf; 88 89 if (!s) 90 return NULL; 91 92 len = strnlen(s, max); 93 buf = kmalloc_track_caller(len+1, gfp); 94 if (buf) { 95 memcpy(buf, s, len); 96 buf[len] = '\0'; 97 } 98 return buf; 99 } 100 EXPORT_SYMBOL(kstrndup); 101 102 /** 103 * kmemdup - duplicate region of memory 104 * 105 * @src: memory region to duplicate 106 * @len: memory region length 107 * @gfp: GFP mask to use 108 */ 109 void *kmemdup(const void *src, size_t len, gfp_t gfp) 110 { 111 void *p; 112 113 p = kmalloc_track_caller(len, gfp); 114 if (p) 115 memcpy(p, src, len); 116 return p; 117 } 118 EXPORT_SYMBOL(kmemdup); 119 120 /** 121 * memdup_user - duplicate memory region from user space 122 * 123 * @src: source address in user space 124 * @len: number of bytes to copy 125 * 126 * Returns an ERR_PTR() on failure. 127 */ 128 void *memdup_user(const void __user *src, size_t len) 129 { 130 void *p; 131 132 /* 133 * Always use GFP_KERNEL, since copy_from_user() can sleep and 134 * cause pagefault, which makes it pointless to use GFP_NOFS 135 * or GFP_ATOMIC. 136 */ 137 p = kmalloc_track_caller(len, GFP_KERNEL); 138 if (!p) 139 return ERR_PTR(-ENOMEM); 140 141 if (copy_from_user(p, src, len)) { 142 kfree(p); 143 return ERR_PTR(-EFAULT); 144 } 145 146 return p; 147 } 148 EXPORT_SYMBOL(memdup_user); 149 150 /* 151 * strndup_user - duplicate an existing string from user space 152 * @s: The string to duplicate 153 * @n: Maximum number of bytes to copy, including the trailing NUL. 154 */ 155 char *strndup_user(const char __user *s, long n) 156 { 157 char *p; 158 long length; 159 160 length = strnlen_user(s, n); 161 162 if (!length) 163 return ERR_PTR(-EFAULT); 164 165 if (length > n) 166 return ERR_PTR(-EINVAL); 167 168 p = memdup_user(s, length); 169 170 if (IS_ERR(p)) 171 return p; 172 173 p[length - 1] = '\0'; 174 175 return p; 176 } 177 EXPORT_SYMBOL(strndup_user); 178 179 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma, 180 struct vm_area_struct *prev, struct rb_node *rb_parent) 181 { 182 struct vm_area_struct *next; 183 184 vma->vm_prev = prev; 185 if (prev) { 186 next = prev->vm_next; 187 prev->vm_next = vma; 188 } else { 189 mm->mmap = vma; 190 if (rb_parent) 191 next = rb_entry(rb_parent, 192 struct vm_area_struct, vm_rb); 193 else 194 next = NULL; 195 } 196 vma->vm_next = next; 197 if (next) 198 next->vm_prev = vma; 199 } 200 201 /* Check if the vma is being used as a stack by this task */ 202 static int vm_is_stack_for_task(struct task_struct *t, 203 struct vm_area_struct *vma) 204 { 205 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t)); 206 } 207 208 /* 209 * Check if the vma is being used as a stack. 210 * If is_group is non-zero, check in the entire thread group or else 211 * just check in the current task. Returns the task_struct of the task 212 * that the vma is stack for. Must be called under rcu_read_lock(). 213 */ 214 struct task_struct *task_of_stack(struct task_struct *task, 215 struct vm_area_struct *vma, bool in_group) 216 { 217 if (vm_is_stack_for_task(task, vma)) 218 return task; 219 220 if (in_group) { 221 struct task_struct *t; 222 223 for_each_thread(task, t) { 224 if (vm_is_stack_for_task(t, vma)) 225 return t; 226 } 227 } 228 229 return NULL; 230 } 231 232 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) 233 void arch_pick_mmap_layout(struct mm_struct *mm) 234 { 235 mm->mmap_base = TASK_UNMAPPED_BASE; 236 mm->get_unmapped_area = arch_get_unmapped_area; 237 } 238 #endif 239 240 /* 241 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall 242 * back to the regular GUP. 243 * If the architecture not support this function, simply return with no 244 * page pinned 245 */ 246 int __weak __get_user_pages_fast(unsigned long start, 247 int nr_pages, int write, struct page **pages) 248 { 249 return 0; 250 } 251 EXPORT_SYMBOL_GPL(__get_user_pages_fast); 252 253 /** 254 * get_user_pages_fast() - pin user pages in memory 255 * @start: starting user address 256 * @nr_pages: number of pages from start to pin 257 * @write: whether pages will be written to 258 * @pages: array that receives pointers to the pages pinned. 259 * Should be at least nr_pages long. 260 * 261 * Returns number of pages pinned. This may be fewer than the number 262 * requested. If nr_pages is 0 or negative, returns 0. If no pages 263 * were pinned, returns -errno. 264 * 265 * get_user_pages_fast provides equivalent functionality to get_user_pages, 266 * operating on current and current->mm, with force=0 and vma=NULL. However 267 * unlike get_user_pages, it must be called without mmap_sem held. 268 * 269 * get_user_pages_fast may take mmap_sem and page table locks, so no 270 * assumptions can be made about lack of locking. get_user_pages_fast is to be 271 * implemented in a way that is advantageous (vs get_user_pages()) when the 272 * user memory area is already faulted in and present in ptes. However if the 273 * pages have to be faulted in, it may turn out to be slightly slower so 274 * callers need to carefully consider what to use. On many architectures, 275 * get_user_pages_fast simply falls back to get_user_pages. 276 */ 277 int __weak get_user_pages_fast(unsigned long start, 278 int nr_pages, int write, struct page **pages) 279 { 280 struct mm_struct *mm = current->mm; 281 return get_user_pages_unlocked(current, mm, start, nr_pages, 282 write, 0, pages); 283 } 284 EXPORT_SYMBOL_GPL(get_user_pages_fast); 285 286 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr, 287 unsigned long len, unsigned long prot, 288 unsigned long flag, unsigned long pgoff) 289 { 290 unsigned long ret; 291 struct mm_struct *mm = current->mm; 292 unsigned long populate; 293 294 ret = security_mmap_file(file, prot, flag); 295 if (!ret) { 296 down_write(&mm->mmap_sem); 297 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff, 298 &populate); 299 up_write(&mm->mmap_sem); 300 if (populate) 301 mm_populate(ret, populate); 302 } 303 return ret; 304 } 305 306 unsigned long vm_mmap(struct file *file, unsigned long addr, 307 unsigned long len, unsigned long prot, 308 unsigned long flag, unsigned long offset) 309 { 310 if (unlikely(offset + PAGE_ALIGN(len) < offset)) 311 return -EINVAL; 312 if (unlikely(offset_in_page(offset))) 313 return -EINVAL; 314 315 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT); 316 } 317 EXPORT_SYMBOL(vm_mmap); 318 319 void kvfree(const void *addr) 320 { 321 if (is_vmalloc_addr(addr)) 322 vfree(addr); 323 else 324 kfree(addr); 325 } 326 EXPORT_SYMBOL(kvfree); 327 328 static inline void *__page_rmapping(struct page *page) 329 { 330 unsigned long mapping; 331 332 mapping = (unsigned long)page->mapping; 333 mapping &= ~PAGE_MAPPING_FLAGS; 334 335 return (void *)mapping; 336 } 337 338 /* Neutral page->mapping pointer to address_space or anon_vma or other */ 339 void *page_rmapping(struct page *page) 340 { 341 page = compound_head(page); 342 return __page_rmapping(page); 343 } 344 345 struct anon_vma *page_anon_vma(struct page *page) 346 { 347 unsigned long mapping; 348 349 page = compound_head(page); 350 mapping = (unsigned long)page->mapping; 351 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) 352 return NULL; 353 return __page_rmapping(page); 354 } 355 356 struct address_space *page_mapping(struct page *page) 357 { 358 unsigned long mapping; 359 360 /* This happens if someone calls flush_dcache_page on slab page */ 361 if (unlikely(PageSlab(page))) 362 return NULL; 363 364 if (unlikely(PageSwapCache(page))) { 365 swp_entry_t entry; 366 367 entry.val = page_private(page); 368 return swap_address_space(entry); 369 } 370 371 mapping = (unsigned long)page->mapping; 372 if (mapping & PAGE_MAPPING_FLAGS) 373 return NULL; 374 return page->mapping; 375 } 376 377 int overcommit_ratio_handler(struct ctl_table *table, int write, 378 void __user *buffer, size_t *lenp, 379 loff_t *ppos) 380 { 381 int ret; 382 383 ret = proc_dointvec(table, write, buffer, lenp, ppos); 384 if (ret == 0 && write) 385 sysctl_overcommit_kbytes = 0; 386 return ret; 387 } 388 389 int overcommit_kbytes_handler(struct ctl_table *table, int write, 390 void __user *buffer, size_t *lenp, 391 loff_t *ppos) 392 { 393 int ret; 394 395 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); 396 if (ret == 0 && write) 397 sysctl_overcommit_ratio = 0; 398 return ret; 399 } 400 401 /* 402 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used 403 */ 404 unsigned long vm_commit_limit(void) 405 { 406 unsigned long allowed; 407 408 if (sysctl_overcommit_kbytes) 409 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10); 410 else 411 allowed = ((totalram_pages - hugetlb_total_pages()) 412 * sysctl_overcommit_ratio / 100); 413 allowed += total_swap_pages; 414 415 return allowed; 416 } 417 418 /** 419 * get_cmdline() - copy the cmdline value to a buffer. 420 * @task: the task whose cmdline value to copy. 421 * @buffer: the buffer to copy to. 422 * @buflen: the length of the buffer. Larger cmdline values are truncated 423 * to this length. 424 * Returns the size of the cmdline field copied. Note that the copy does 425 * not guarantee an ending NULL byte. 426 */ 427 int get_cmdline(struct task_struct *task, char *buffer, int buflen) 428 { 429 int res = 0; 430 unsigned int len; 431 struct mm_struct *mm = get_task_mm(task); 432 if (!mm) 433 goto out; 434 if (!mm->arg_end) 435 goto out_mm; /* Shh! No looking before we're done */ 436 437 len = mm->arg_end - mm->arg_start; 438 439 if (len > buflen) 440 len = buflen; 441 442 res = access_process_vm(task, mm->arg_start, buffer, len, 0); 443 444 /* 445 * If the nul at the end of args has been overwritten, then 446 * assume application is using setproctitle(3). 447 */ 448 if (res > 0 && buffer[res-1] != '\0' && len < buflen) { 449 len = strnlen(buffer, res); 450 if (len < res) { 451 res = len; 452 } else { 453 len = mm->env_end - mm->env_start; 454 if (len > buflen - res) 455 len = buflen - res; 456 res += access_process_vm(task, mm->env_start, 457 buffer+res, len, 0); 458 res = strnlen(buffer, res); 459 } 460 } 461 out_mm: 462 mmput(mm); 463 out: 464 return res; 465 } 466