1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * linux/mm/process_vm_access.c 4 * 5 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp. 6 */ 7 8 #include <linux/mm.h> 9 #include <linux/uio.h> 10 #include <linux/sched.h> 11 #include <linux/sched/mm.h> 12 #include <linux/highmem.h> 13 #include <linux/ptrace.h> 14 #include <linux/slab.h> 15 #include <linux/syscalls.h> 16 17 /** 18 * process_vm_rw_pages - read/write pages from task specified 19 * @pages: array of pointers to pages we want to copy 20 * @offset: offset in page to start copying from/to 21 * @len: number of bytes to copy 22 * @iter: where to copy to/from locally 23 * @vm_write: 0 means copy from, 1 means copy to 24 * Returns 0 on success, error code otherwise 25 */ 26 static int process_vm_rw_pages(struct page **pages, 27 unsigned offset, 28 size_t len, 29 struct iov_iter *iter, 30 int vm_write) 31 { 32 /* Do the copy for each page */ 33 while (len && iov_iter_count(iter)) { 34 struct page *page = *pages++; 35 size_t copy = PAGE_SIZE - offset; 36 size_t copied; 37 38 if (copy > len) 39 copy = len; 40 41 if (vm_write) 42 copied = copy_page_from_iter(page, offset, copy, iter); 43 else 44 copied = copy_page_to_iter(page, offset, copy, iter); 45 46 len -= copied; 47 if (copied < copy && iov_iter_count(iter)) 48 return -EFAULT; 49 offset = 0; 50 } 51 return 0; 52 } 53 54 /* Maximum number of pages kmalloc'd to hold struct page's during copy */ 55 #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2) 56 57 /** 58 * process_vm_rw_single_vec - read/write pages from task specified 59 * @addr: start memory address of target process 60 * @len: size of area to copy to/from 61 * @iter: where to copy to/from locally 62 * @process_pages: struct pages area that can store at least 63 * nr_pages_to_copy struct page pointers 64 * @mm: mm for task 65 * @task: task to read/write from 66 * @vm_write: 0 means copy from, 1 means copy to 67 * Returns 0 on success or on failure error code 68 */ 69 static int process_vm_rw_single_vec(unsigned long addr, 70 unsigned long len, 71 struct iov_iter *iter, 72 struct page **process_pages, 73 struct mm_struct *mm, 74 struct task_struct *task, 75 int vm_write) 76 { 77 unsigned long pa = addr & PAGE_MASK; 78 unsigned long start_offset = addr - pa; 79 unsigned long nr_pages; 80 ssize_t rc = 0; 81 unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES 82 / sizeof(struct pages *); 83 unsigned int flags = 0; 84 85 /* Work out address and page range required */ 86 if (len == 0) 87 return 0; 88 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; 89 90 if (vm_write) 91 flags |= FOLL_WRITE; 92 93 while (!rc && nr_pages && iov_iter_count(iter)) { 94 int pinned_pages = min(nr_pages, max_pages_per_loop); 95 int locked = 1; 96 size_t bytes; 97 98 /* 99 * Get the pages we're interested in. We must 100 * access remotely because task/mm might not 101 * current/current->mm 102 */ 103 mmap_read_lock(mm); 104 pinned_pages = pin_user_pages_remote(mm, pa, pinned_pages, 105 flags, process_pages, 106 NULL, &locked); 107 if (locked) 108 mmap_read_unlock(mm); 109 if (pinned_pages <= 0) 110 return -EFAULT; 111 112 bytes = pinned_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 -= pinned_pages; 122 pa += pinned_pages * PAGE_SIZE; 123 124 /* If vm_write is set, the pages need to be made dirty: */ 125 unpin_user_pages_dirty_lock(process_pages, pinned_pages, 126 vm_write); 127 } 128 129 return rc; 130 } 131 132 /* Maximum number of entries for process pages array 133 which lives on stack */ 134 #define PVM_MAX_PP_ARRAY_COUNT 16 135 136 /** 137 * process_vm_rw_core - core of reading/writing pages from task specified 138 * @pid: PID of process to read/write from/to 139 * @iter: where to copy to/from locally 140 * @rvec: iovec array specifying where to copy to/from in the other process 141 * @riovcnt: size of rvec array 142 * @flags: currently unused 143 * @vm_write: 0 if reading from other process, 1 if writing to other process 144 * 145 * Returns the number of bytes read/written or error code. May 146 * return less bytes than expected if an error occurs during the copying 147 * process. 148 */ 149 static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, 150 const struct iovec *rvec, 151 unsigned long riovcnt, 152 unsigned long flags, int vm_write) 153 { 154 struct task_struct *task; 155 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; 156 struct page **process_pages = pp_stack; 157 struct mm_struct *mm; 158 unsigned long i; 159 ssize_t rc = 0; 160 unsigned long nr_pages = 0; 161 unsigned long nr_pages_iov; 162 ssize_t iov_len; 163 size_t total_len = iov_iter_count(iter); 164 165 /* 166 * Work out how many pages of struct pages we're going to need 167 * when eventually calling get_user_pages 168 */ 169 for (i = 0; i < riovcnt; i++) { 170 iov_len = rvec[i].iov_len; 171 if (iov_len > 0) { 172 nr_pages_iov = ((unsigned long)rvec[i].iov_base 173 + iov_len) 174 / PAGE_SIZE - (unsigned long)rvec[i].iov_base 175 / PAGE_SIZE + 1; 176 nr_pages = max(nr_pages, nr_pages_iov); 177 } 178 } 179 180 if (nr_pages == 0) 181 return 0; 182 183 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { 184 /* For reliability don't try to kmalloc more than 185 2 pages worth */ 186 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, 187 sizeof(struct pages *)*nr_pages), 188 GFP_KERNEL); 189 190 if (!process_pages) 191 return -ENOMEM; 192 } 193 194 /* Get process information */ 195 task = find_get_task_by_vpid(pid); 196 if (!task) { 197 rc = -ESRCH; 198 goto free_proc_pages; 199 } 200 201 mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); 202 if (!mm || IS_ERR(mm)) { 203 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; 204 /* 205 * Explicitly map EACCES to EPERM as EPERM is a more 206 * appropriate error code for process_vw_readv/writev 207 */ 208 if (rc == -EACCES) 209 rc = -EPERM; 210 goto put_task_struct; 211 } 212 213 for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++) 214 rc = process_vm_rw_single_vec( 215 (unsigned long)rvec[i].iov_base, rvec[i].iov_len, 216 iter, process_pages, mm, task, vm_write); 217 218 /* copied = space before - space after */ 219 total_len -= iov_iter_count(iter); 220 221 /* If we have managed to copy any data at all then 222 we return the number of bytes copied. Otherwise 223 we return the error code */ 224 if (total_len) 225 rc = total_len; 226 227 mmput(mm); 228 229 put_task_struct: 230 put_task_struct(task); 231 232 free_proc_pages: 233 if (process_pages != pp_stack) 234 kfree(process_pages); 235 return rc; 236 } 237 238 /** 239 * process_vm_rw - check iovecs before calling core routine 240 * @pid: PID of process to read/write from/to 241 * @lvec: iovec array specifying where to copy to/from locally 242 * @liovcnt: size of lvec array 243 * @rvec: iovec array specifying where to copy to/from in the other process 244 * @riovcnt: size of rvec array 245 * @flags: currently unused 246 * @vm_write: 0 if reading from other process, 1 if writing to other process 247 * 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_iov_l; 276 iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, false); 277 if (IS_ERR(iov_r)) { 278 rc = PTR_ERR(iov_r); 279 goto free_iov_l; 280 } 281 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); 282 if (iov_r != iovstack_r) 283 kfree(iov_r); 284 free_iov_l: 285 kfree(iov_l); 286 return rc; 287 } 288 289 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, 290 unsigned long, liovcnt, const struct iovec __user *, rvec, 291 unsigned long, riovcnt, unsigned long, flags) 292 { 293 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0); 294 } 295 296 SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, 297 const struct iovec __user *, lvec, 298 unsigned long, liovcnt, const struct iovec __user *, rvec, 299 unsigned long, riovcnt, unsigned long, flags) 300 { 301 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1); 302 } 303