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