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