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 92 /* Work out address and page range required */ 93 if (len == 0) 94 return 0; 95 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; 96 97 while (!rc && nr_pages && iov_iter_count(iter)) { 98 int pages = min(nr_pages, max_pages_per_loop); 99 size_t bytes; 100 101 /* 102 * Get the pages we're interested in. We must 103 * add FOLL_REMOTE because task/mm might not 104 * current/current->mm 105 */ 106 pages = __get_user_pages_unlocked(task, mm, pa, pages, 107 vm_write, 0, process_pages, 108 FOLL_REMOTE); 109 if (pages <= 0) 110 return -EFAULT; 111 112 bytes = pages * PAGE_SIZE - start_offset; 113 if (bytes > len) 114 bytes = len; 115 116 rc = process_vm_rw_pages(process_pages, 117 start_offset, bytes, iter, 118 vm_write); 119 len -= bytes; 120 start_offset = 0; 121 nr_pages -= pages; 122 pa += pages * PAGE_SIZE; 123 while (pages) 124 put_page(process_pages[--pages]); 125 } 126 127 return rc; 128 } 129 130 /* Maximum number of entries for process pages array 131 which lives on stack */ 132 #define PVM_MAX_PP_ARRAY_COUNT 16 133 134 /** 135 * process_vm_rw_core - core of reading/writing pages from task specified 136 * @pid: PID of process to read/write from/to 137 * @iter: where to copy to/from locally 138 * @rvec: iovec array specifying where to copy to/from in the other process 139 * @riovcnt: size of rvec array 140 * @flags: currently unused 141 * @vm_write: 0 if reading from other process, 1 if writing to other process 142 * Returns the number of bytes read/written or error code. May 143 * return less bytes than expected if an error occurs during the copying 144 * process. 145 */ 146 static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, 147 const struct iovec *rvec, 148 unsigned long riovcnt, 149 unsigned long flags, int vm_write) 150 { 151 struct task_struct *task; 152 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; 153 struct page **process_pages = pp_stack; 154 struct mm_struct *mm; 155 unsigned long i; 156 ssize_t rc = 0; 157 unsigned long nr_pages = 0; 158 unsigned long nr_pages_iov; 159 ssize_t iov_len; 160 size_t total_len = iov_iter_count(iter); 161 162 /* 163 * Work out how many pages of struct pages we're going to need 164 * when eventually calling get_user_pages 165 */ 166 for (i = 0; i < riovcnt; i++) { 167 iov_len = rvec[i].iov_len; 168 if (iov_len > 0) { 169 nr_pages_iov = ((unsigned long)rvec[i].iov_base 170 + iov_len) 171 / PAGE_SIZE - (unsigned long)rvec[i].iov_base 172 / PAGE_SIZE + 1; 173 nr_pages = max(nr_pages, nr_pages_iov); 174 } 175 } 176 177 if (nr_pages == 0) 178 return 0; 179 180 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { 181 /* For reliability don't try to kmalloc more than 182 2 pages worth */ 183 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, 184 sizeof(struct pages *)*nr_pages), 185 GFP_KERNEL); 186 187 if (!process_pages) 188 return -ENOMEM; 189 } 190 191 /* Get process information */ 192 rcu_read_lock(); 193 task = find_task_by_vpid(pid); 194 if (task) 195 get_task_struct(task); 196 rcu_read_unlock(); 197 if (!task) { 198 rc = -ESRCH; 199 goto free_proc_pages; 200 } 201 202 mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); 203 if (!mm || IS_ERR(mm)) { 204 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; 205 /* 206 * Explicitly map EACCES to EPERM as EPERM is a more a 207 * appropriate error code for process_vw_readv/writev 208 */ 209 if (rc == -EACCES) 210 rc = -EPERM; 211 goto put_task_struct; 212 } 213 214 for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++) 215 rc = process_vm_rw_single_vec( 216 (unsigned long)rvec[i].iov_base, rvec[i].iov_len, 217 iter, process_pages, mm, task, vm_write); 218 219 /* copied = space before - space after */ 220 total_len -= iov_iter_count(iter); 221 222 /* If we have managed to copy any data at all then 223 we return the number of bytes copied. Otherwise 224 we return the error code */ 225 if (total_len) 226 rc = total_len; 227 228 mmput(mm); 229 230 put_task_struct: 231 put_task_struct(task); 232 233 free_proc_pages: 234 if (process_pages != pp_stack) 235 kfree(process_pages); 236 return rc; 237 } 238 239 /** 240 * process_vm_rw - check iovecs before calling core routine 241 * @pid: PID of process to read/write from/to 242 * @lvec: iovec array specifying where to copy to/from locally 243 * @liovcnt: size of lvec array 244 * @rvec: iovec array specifying where to copy to/from in the other process 245 * @riovcnt: size of rvec array 246 * @flags: currently unused 247 * @vm_write: 0 if reading from other process, 1 if writing to other process 248 * Returns the number of bytes read/written or error code. May 249 * return less bytes than expected if an error occurs during the copying 250 * process. 251 */ 252 static ssize_t process_vm_rw(pid_t pid, 253 const struct iovec __user *lvec, 254 unsigned long liovcnt, 255 const struct iovec __user *rvec, 256 unsigned long riovcnt, 257 unsigned long flags, int vm_write) 258 { 259 struct iovec iovstack_l[UIO_FASTIOV]; 260 struct iovec iovstack_r[UIO_FASTIOV]; 261 struct iovec *iov_l = iovstack_l; 262 struct iovec *iov_r = iovstack_r; 263 struct iov_iter iter; 264 ssize_t rc; 265 int dir = vm_write ? WRITE : READ; 266 267 if (flags != 0) 268 return -EINVAL; 269 270 /* Check iovecs */ 271 rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); 272 if (rc < 0) 273 return rc; 274 if (!iov_iter_count(&iter)) 275 goto free_iovecs; 276 277 rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV, 278 iovstack_r, &iov_r); 279 if (rc <= 0) 280 goto free_iovecs; 281 282 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); 283 284 free_iovecs: 285 if (iov_r != iovstack_r) 286 kfree(iov_r); 287 kfree(iov_l); 288 289 return rc; 290 } 291 292 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, 293 unsigned long, liovcnt, const struct iovec __user *, rvec, 294 unsigned long, riovcnt, unsigned long, flags) 295 { 296 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0); 297 } 298 299 SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, 300 const struct iovec __user *, lvec, 301 unsigned long, liovcnt, const struct iovec __user *, rvec, 302 unsigned long, riovcnt, unsigned long, flags) 303 { 304 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1); 305 } 306 307 #ifdef CONFIG_COMPAT 308 309 static ssize_t 310 compat_process_vm_rw(compat_pid_t pid, 311 const struct compat_iovec __user *lvec, 312 unsigned long liovcnt, 313 const struct compat_iovec __user *rvec, 314 unsigned long riovcnt, 315 unsigned long flags, int vm_write) 316 { 317 struct iovec iovstack_l[UIO_FASTIOV]; 318 struct iovec iovstack_r[UIO_FASTIOV]; 319 struct iovec *iov_l = iovstack_l; 320 struct iovec *iov_r = iovstack_r; 321 struct iov_iter iter; 322 ssize_t rc = -EFAULT; 323 int dir = vm_write ? WRITE : READ; 324 325 if (flags != 0) 326 return -EINVAL; 327 328 rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); 329 if (rc < 0) 330 return rc; 331 if (!iov_iter_count(&iter)) 332 goto free_iovecs; 333 rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, 334 UIO_FASTIOV, iovstack_r, 335 &iov_r); 336 if (rc <= 0) 337 goto free_iovecs; 338 339 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); 340 341 free_iovecs: 342 if (iov_r != iovstack_r) 343 kfree(iov_r); 344 kfree(iov_l); 345 return rc; 346 } 347 348 COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid, 349 const struct compat_iovec __user *, lvec, 350 compat_ulong_t, liovcnt, 351 const struct compat_iovec __user *, rvec, 352 compat_ulong_t, riovcnt, 353 compat_ulong_t, flags) 354 { 355 return compat_process_vm_rw(pid, lvec, liovcnt, rvec, 356 riovcnt, flags, 0); 357 } 358 359 COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid, 360 const struct compat_iovec __user *, lvec, 361 compat_ulong_t, liovcnt, 362 const struct compat_iovec __user *, rvec, 363 compat_ulong_t, riovcnt, 364 compat_ulong_t, flags) 365 { 366 return compat_process_vm_rw(pid, lvec, liovcnt, rvec, 367 riovcnt, flags, 1); 368 } 369 370 #endif 371