1 /* 2 * linux/mm/process_vm_access.c 3 * 4 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp. 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/mm.h> 13 #include <linux/uio.h> 14 #include <linux/sched.h> 15 #include <linux/highmem.h> 16 #include <linux/ptrace.h> 17 #include <linux/slab.h> 18 #include <linux/syscalls.h> 19 20 #ifdef CONFIG_COMPAT 21 #include <linux/compat.h> 22 #endif 23 24 /** 25 * process_vm_rw_pages - read/write pages from task specified 26 * @pages: array of pointers to pages we want to copy 27 * @start_offset: offset in page to start copying from/to 28 * @len: number of bytes to copy 29 * @iter: where to copy to/from locally 30 * @vm_write: 0 means copy from, 1 means copy to 31 * Returns 0 on success, error code otherwise 32 */ 33 static int process_vm_rw_pages(struct page **pages, 34 unsigned offset, 35 size_t len, 36 struct iov_iter *iter, 37 int vm_write) 38 { 39 /* Do the copy for each page */ 40 while (len && iov_iter_count(iter)) { 41 struct page *page = *pages++; 42 size_t copy = PAGE_SIZE - offset; 43 size_t copied; 44 45 if (copy > len) 46 copy = len; 47 48 if (vm_write) { 49 copied = copy_page_from_iter(page, offset, copy, iter); 50 set_page_dirty_lock(page); 51 } else { 52 copied = copy_page_to_iter(page, offset, copy, iter); 53 } 54 len -= copied; 55 if (copied < copy && iov_iter_count(iter)) 56 return -EFAULT; 57 offset = 0; 58 } 59 return 0; 60 } 61 62 /* Maximum number of pages kmalloc'd to hold struct page's during copy */ 63 #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2) 64 65 /** 66 * process_vm_rw_single_vec - read/write pages from task specified 67 * @addr: start memory address of target process 68 * @len: size of area to copy to/from 69 * @iter: where to copy to/from locally 70 * @process_pages: struct pages area that can store at least 71 * nr_pages_to_copy struct page pointers 72 * @mm: mm for task 73 * @task: task to read/write from 74 * @vm_write: 0 means copy from, 1 means copy to 75 * Returns 0 on success or on failure error code 76 */ 77 static int process_vm_rw_single_vec(unsigned long addr, 78 unsigned long len, 79 struct iov_iter *iter, 80 struct page **process_pages, 81 struct mm_struct *mm, 82 struct task_struct *task, 83 int vm_write) 84 { 85 unsigned long pa = addr & PAGE_MASK; 86 unsigned long start_offset = addr - pa; 87 unsigned long nr_pages; 88 ssize_t rc = 0; 89 unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES 90 / sizeof(struct pages *); 91 unsigned int flags = 0; 92 93 /* Work out address and page range required */ 94 if (len == 0) 95 return 0; 96 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; 97 98 if (vm_write) 99 flags |= FOLL_WRITE; 100 101 while (!rc && nr_pages && iov_iter_count(iter)) { 102 int pages = min(nr_pages, max_pages_per_loop); 103 int locked = 1; 104 size_t bytes; 105 106 /* 107 * Get the pages we're interested in. We must 108 * access remotely because task/mm might not 109 * current/current->mm 110 */ 111 down_read(&mm->mmap_sem); 112 pages = get_user_pages_remote(task, mm, pa, pages, flags, 113 process_pages, NULL, &locked); 114 if (locked) 115 up_read(&mm->mmap_sem); 116 if (pages <= 0) 117 return -EFAULT; 118 119 bytes = pages * PAGE_SIZE - start_offset; 120 if (bytes > len) 121 bytes = len; 122 123 rc = process_vm_rw_pages(process_pages, 124 start_offset, bytes, iter, 125 vm_write); 126 len -= bytes; 127 start_offset = 0; 128 nr_pages -= pages; 129 pa += pages * PAGE_SIZE; 130 while (pages) 131 put_page(process_pages[--pages]); 132 } 133 134 return rc; 135 } 136 137 /* Maximum number of entries for process pages array 138 which lives on stack */ 139 #define PVM_MAX_PP_ARRAY_COUNT 16 140 141 /** 142 * process_vm_rw_core - core of reading/writing pages from task specified 143 * @pid: PID of process to read/write from/to 144 * @iter: where to copy to/from locally 145 * @rvec: iovec array specifying where to copy to/from in the other process 146 * @riovcnt: size of rvec array 147 * @flags: currently unused 148 * @vm_write: 0 if reading from other process, 1 if writing to other process 149 * Returns the number of bytes read/written or error code. May 150 * return less bytes than expected if an error occurs during the copying 151 * process. 152 */ 153 static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, 154 const struct iovec *rvec, 155 unsigned long riovcnt, 156 unsigned long flags, int vm_write) 157 { 158 struct task_struct *task; 159 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; 160 struct page **process_pages = pp_stack; 161 struct mm_struct *mm; 162 unsigned long i; 163 ssize_t rc = 0; 164 unsigned long nr_pages = 0; 165 unsigned long nr_pages_iov; 166 ssize_t iov_len; 167 size_t total_len = iov_iter_count(iter); 168 169 /* 170 * Work out how many pages of struct pages we're going to need 171 * when eventually calling get_user_pages 172 */ 173 for (i = 0; i < riovcnt; i++) { 174 iov_len = rvec[i].iov_len; 175 if (iov_len > 0) { 176 nr_pages_iov = ((unsigned long)rvec[i].iov_base 177 + iov_len) 178 / PAGE_SIZE - (unsigned long)rvec[i].iov_base 179 / PAGE_SIZE + 1; 180 nr_pages = max(nr_pages, nr_pages_iov); 181 } 182 } 183 184 if (nr_pages == 0) 185 return 0; 186 187 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { 188 /* For reliability don't try to kmalloc more than 189 2 pages worth */ 190 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, 191 sizeof(struct pages *)*nr_pages), 192 GFP_KERNEL); 193 194 if (!process_pages) 195 return -ENOMEM; 196 } 197 198 /* Get process information */ 199 rcu_read_lock(); 200 task = find_task_by_vpid(pid); 201 if (task) 202 get_task_struct(task); 203 rcu_read_unlock(); 204 if (!task) { 205 rc = -ESRCH; 206 goto free_proc_pages; 207 } 208 209 mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); 210 if (!mm || IS_ERR(mm)) { 211 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; 212 /* 213 * Explicitly map EACCES to EPERM as EPERM is a more a 214 * appropriate error code for process_vw_readv/writev 215 */ 216 if (rc == -EACCES) 217 rc = -EPERM; 218 goto put_task_struct; 219 } 220 221 for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++) 222 rc = process_vm_rw_single_vec( 223 (unsigned long)rvec[i].iov_base, rvec[i].iov_len, 224 iter, process_pages, mm, task, vm_write); 225 226 /* copied = space before - space after */ 227 total_len -= iov_iter_count(iter); 228 229 /* If we have managed to copy any data at all then 230 we return the number of bytes copied. Otherwise 231 we return the error code */ 232 if (total_len) 233 rc = total_len; 234 235 mmput(mm); 236 237 put_task_struct: 238 put_task_struct(task); 239 240 free_proc_pages: 241 if (process_pages != pp_stack) 242 kfree(process_pages); 243 return rc; 244 } 245 246 /** 247 * process_vm_rw - check iovecs before calling core routine 248 * @pid: PID of process to read/write from/to 249 * @lvec: iovec array specifying where to copy to/from locally 250 * @liovcnt: size of lvec array 251 * @rvec: iovec array specifying where to copy to/from in the other process 252 * @riovcnt: size of rvec array 253 * @flags: currently unused 254 * @vm_write: 0 if reading from other process, 1 if writing to other process 255 * Returns the number of bytes read/written or error code. May 256 * return less bytes than expected if an error occurs during the copying 257 * process. 258 */ 259 static ssize_t process_vm_rw(pid_t pid, 260 const struct iovec __user *lvec, 261 unsigned long liovcnt, 262 const struct iovec __user *rvec, 263 unsigned long riovcnt, 264 unsigned long flags, int vm_write) 265 { 266 struct iovec iovstack_l[UIO_FASTIOV]; 267 struct iovec iovstack_r[UIO_FASTIOV]; 268 struct iovec *iov_l = iovstack_l; 269 struct iovec *iov_r = iovstack_r; 270 struct iov_iter iter; 271 ssize_t rc; 272 int dir = vm_write ? WRITE : READ; 273 274 if (flags != 0) 275 return -EINVAL; 276 277 /* Check iovecs */ 278 rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); 279 if (rc < 0) 280 return rc; 281 if (!iov_iter_count(&iter)) 282 goto free_iovecs; 283 284 rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV, 285 iovstack_r, &iov_r); 286 if (rc <= 0) 287 goto free_iovecs; 288 289 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); 290 291 free_iovecs: 292 if (iov_r != iovstack_r) 293 kfree(iov_r); 294 kfree(iov_l); 295 296 return rc; 297 } 298 299 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, 300 unsigned long, liovcnt, const struct iovec __user *, rvec, 301 unsigned long, riovcnt, unsigned long, flags) 302 { 303 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0); 304 } 305 306 SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, 307 const struct iovec __user *, lvec, 308 unsigned long, liovcnt, const struct iovec __user *, rvec, 309 unsigned long, riovcnt, unsigned long, flags) 310 { 311 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1); 312 } 313 314 #ifdef CONFIG_COMPAT 315 316 static ssize_t 317 compat_process_vm_rw(compat_pid_t pid, 318 const struct compat_iovec __user *lvec, 319 unsigned long liovcnt, 320 const struct compat_iovec __user *rvec, 321 unsigned long riovcnt, 322 unsigned long flags, int vm_write) 323 { 324 struct iovec iovstack_l[UIO_FASTIOV]; 325 struct iovec iovstack_r[UIO_FASTIOV]; 326 struct iovec *iov_l = iovstack_l; 327 struct iovec *iov_r = iovstack_r; 328 struct iov_iter iter; 329 ssize_t rc = -EFAULT; 330 int dir = vm_write ? WRITE : READ; 331 332 if (flags != 0) 333 return -EINVAL; 334 335 rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); 336 if (rc < 0) 337 return rc; 338 if (!iov_iter_count(&iter)) 339 goto free_iovecs; 340 rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, 341 UIO_FASTIOV, iovstack_r, 342 &iov_r); 343 if (rc <= 0) 344 goto free_iovecs; 345 346 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); 347 348 free_iovecs: 349 if (iov_r != iovstack_r) 350 kfree(iov_r); 351 kfree(iov_l); 352 return rc; 353 } 354 355 COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid, 356 const struct compat_iovec __user *, lvec, 357 compat_ulong_t, liovcnt, 358 const struct compat_iovec __user *, rvec, 359 compat_ulong_t, riovcnt, 360 compat_ulong_t, flags) 361 { 362 return compat_process_vm_rw(pid, lvec, liovcnt, rvec, 363 riovcnt, flags, 0); 364 } 365 366 COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid, 367 const struct compat_iovec __user *, lvec, 368 compat_ulong_t, liovcnt, 369 const struct compat_iovec __user *, rvec, 370 compat_ulong_t, riovcnt, 371 compat_ulong_t, flags) 372 { 373 return compat_process_vm_rw(pid, lvec, liovcnt, rvec, 374 riovcnt, flags, 1); 375 } 376 377 #endif 378