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/compat.h> 9 #include <linux/mm.h> 10 #include <linux/uio.h> 11 #include <linux/sched.h> 12 #include <linux/sched/mm.h> 13 #include <linux/highmem.h> 14 #include <linux/ptrace.h> 15 #include <linux/slab.h> 16 #include <linux/syscalls.h> 17 18 /** 19 * process_vm_rw_pages - read/write pages from task specified 20 * @pages: array of pointers to pages we want to copy 21 * @offset: offset in page to start copying from/to 22 * @len: number of bytes to copy 23 * @iter: where to copy to/from locally 24 * @vm_write: 0 means copy from, 1 means copy to 25 * Returns 0 on success, error code otherwise 26 */ 27 static int process_vm_rw_pages(struct page **pages, 28 unsigned offset, 29 size_t len, 30 struct iov_iter *iter, 31 int vm_write) 32 { 33 /* Do the copy for each page */ 34 while (len && iov_iter_count(iter)) { 35 struct page *page = *pages++; 36 size_t copy = PAGE_SIZE - offset; 37 size_t copied; 38 39 if (copy > len) 40 copy = len; 41 42 if (vm_write) 43 copied = copy_page_from_iter(page, offset, copy, iter); 44 else 45 copied = copy_page_to_iter(page, offset, copy, iter); 46 47 len -= copied; 48 if (copied < copy && iov_iter_count(iter)) 49 return -EFAULT; 50 offset = 0; 51 } 52 return 0; 53 } 54 55 /* Maximum number of pages kmalloc'd to hold struct page's during copy */ 56 #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2) 57 58 /** 59 * process_vm_rw_single_vec - read/write pages from task specified 60 * @addr: start memory address of target process 61 * @len: size of area to copy to/from 62 * @iter: where to copy to/from locally 63 * @process_pages: struct pages area that can store at least 64 * nr_pages_to_copy struct page pointers 65 * @mm: mm for task 66 * @task: task to read/write from 67 * @vm_write: 0 means copy from, 1 means copy to 68 * Returns 0 on success or on failure error code 69 */ 70 static int process_vm_rw_single_vec(unsigned long addr, 71 unsigned long len, 72 struct iov_iter *iter, 73 struct page **process_pages, 74 struct mm_struct *mm, 75 struct task_struct *task, 76 int vm_write) 77 { 78 unsigned long pa = addr & PAGE_MASK; 79 unsigned long start_offset = addr - pa; 80 unsigned long nr_pages; 81 ssize_t rc = 0; 82 unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES 83 / sizeof(struct pages *); 84 unsigned int flags = 0; 85 86 /* Work out address and page range required */ 87 if (len == 0) 88 return 0; 89 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; 90 91 if (vm_write) 92 flags |= FOLL_WRITE; 93 94 while (!rc && nr_pages && iov_iter_count(iter)) { 95 int pinned_pages = min(nr_pages, max_pages_per_loop); 96 int locked = 1; 97 size_t bytes; 98 99 /* 100 * Get the pages we're interested in. We must 101 * access remotely because task/mm might not 102 * current/current->mm 103 */ 104 mmap_read_lock(mm); 105 pinned_pages = pin_user_pages_remote(mm, pa, pinned_pages, 106 flags, process_pages, 107 NULL, &locked); 108 if (locked) 109 mmap_read_unlock(mm); 110 if (pinned_pages <= 0) 111 return -EFAULT; 112 113 bytes = pinned_pages * PAGE_SIZE - start_offset; 114 if (bytes > len) 115 bytes = len; 116 117 rc = process_vm_rw_pages(process_pages, 118 start_offset, bytes, iter, 119 vm_write); 120 len -= bytes; 121 start_offset = 0; 122 nr_pages -= pinned_pages; 123 pa += pinned_pages * PAGE_SIZE; 124 125 /* If vm_write is set, the pages need to be made dirty: */ 126 unpin_user_pages_dirty_lock(process_pages, pinned_pages, 127 vm_write); 128 } 129 130 return rc; 131 } 132 133 /* Maximum number of entries for process pages array 134 which lives on stack */ 135 #define PVM_MAX_PP_ARRAY_COUNT 16 136 137 /** 138 * process_vm_rw_core - core of reading/writing pages from task specified 139 * @pid: PID of process to read/write from/to 140 * @iter: where to copy to/from locally 141 * @rvec: iovec array specifying where to copy to/from in the other process 142 * @riovcnt: size of rvec array 143 * @flags: currently unused 144 * @vm_write: 0 if reading from other process, 1 if writing to other process 145 * 146 * Returns the number of bytes read/written or error code. May 147 * return less bytes than expected if an error occurs during the copying 148 * process. 149 */ 150 static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, 151 const struct iovec *rvec, 152 unsigned long riovcnt, 153 unsigned long flags, int vm_write) 154 { 155 struct task_struct *task; 156 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; 157 struct page **process_pages = pp_stack; 158 struct mm_struct *mm; 159 unsigned long i; 160 ssize_t rc = 0; 161 unsigned long nr_pages = 0; 162 unsigned long nr_pages_iov; 163 ssize_t iov_len; 164 size_t total_len = iov_iter_count(iter); 165 166 /* 167 * Work out how many pages of struct pages we're going to need 168 * when eventually calling get_user_pages 169 */ 170 for (i = 0; i < riovcnt; i++) { 171 iov_len = rvec[i].iov_len; 172 if (iov_len > 0) { 173 nr_pages_iov = ((unsigned long)rvec[i].iov_base 174 + iov_len) 175 / PAGE_SIZE - (unsigned long)rvec[i].iov_base 176 / PAGE_SIZE + 1; 177 nr_pages = max(nr_pages, nr_pages_iov); 178 } 179 } 180 181 if (nr_pages == 0) 182 return 0; 183 184 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { 185 /* For reliability don't try to kmalloc more than 186 2 pages worth */ 187 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, 188 sizeof(struct pages *)*nr_pages), 189 GFP_KERNEL); 190 191 if (!process_pages) 192 return -ENOMEM; 193 } 194 195 /* Get process information */ 196 task = find_get_task_by_vpid(pid); 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 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 * 249 * Returns the number of bytes read/written or error code. May 250 * return less bytes than expected if an error occurs during the copying 251 * process. 252 */ 253 static ssize_t process_vm_rw(pid_t pid, 254 const struct iovec __user *lvec, 255 unsigned long liovcnt, 256 const struct iovec __user *rvec, 257 unsigned long riovcnt, 258 unsigned long flags, int vm_write) 259 { 260 struct iovec iovstack_l[UIO_FASTIOV]; 261 struct iovec iovstack_r[UIO_FASTIOV]; 262 struct iovec *iov_l = iovstack_l; 263 struct iovec *iov_r; 264 struct iov_iter iter; 265 ssize_t rc; 266 int dir = vm_write ? WRITE : READ; 267 268 if (flags != 0) 269 return -EINVAL; 270 271 /* Check iovecs */ 272 rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); 273 if (rc < 0) 274 return rc; 275 if (!iov_iter_count(&iter)) 276 goto free_iov_l; 277 iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, 278 in_compat_syscall()); 279 if (IS_ERR(iov_r)) { 280 rc = PTR_ERR(iov_r); 281 goto free_iov_l; 282 } 283 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); 284 if (iov_r != iovstack_r) 285 kfree(iov_r); 286 free_iov_l: 287 kfree(iov_l); 288 return rc; 289 } 290 291 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, 292 unsigned long, liovcnt, const struct iovec __user *, rvec, 293 unsigned long, riovcnt, unsigned long, flags) 294 { 295 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0); 296 } 297 298 SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, 299 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, 1); 304 } 305