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 2 57 58 /* Maximum number of pages that can be stored at a time */ 59 #define PVM_MAX_USER_PAGES (PVM_MAX_KMALLOC_PAGES * PAGE_SIZE / sizeof(struct page *)) 60 61 /** 62 * process_vm_rw_single_vec - read/write pages from task specified 63 * @addr: start memory address of target process 64 * @len: size of area to copy to/from 65 * @iter: where to copy to/from locally 66 * @process_pages: struct pages area that can store at least 67 * nr_pages_to_copy struct page pointers 68 * @mm: mm for task 69 * @task: task to read/write from 70 * @vm_write: 0 means copy from, 1 means copy to 71 * Returns 0 on success or on failure error code 72 */ 73 static int process_vm_rw_single_vec(unsigned long addr, 74 unsigned long len, 75 struct iov_iter *iter, 76 struct page **process_pages, 77 struct mm_struct *mm, 78 struct task_struct *task, 79 int vm_write) 80 { 81 unsigned long pa = addr & PAGE_MASK; 82 unsigned long start_offset = addr - pa; 83 unsigned long nr_pages; 84 ssize_t rc = 0; 85 unsigned int flags = 0; 86 87 /* Work out address and page range required */ 88 if (len == 0) 89 return 0; 90 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; 91 92 if (vm_write) 93 flags |= FOLL_WRITE; 94 95 while (!rc && nr_pages && iov_iter_count(iter)) { 96 int pinned_pages = min_t(unsigned long, nr_pages, PVM_MAX_USER_PAGES); 97 int locked = 1; 98 size_t bytes; 99 100 /* 101 * Get the pages we're interested in. We must 102 * access remotely because task/mm might not 103 * current/current->mm 104 */ 105 mmap_read_lock(mm); 106 pinned_pages = pin_user_pages_remote(mm, pa, pinned_pages, 107 flags, process_pages, 108 &locked); 109 if (locked) 110 mmap_read_unlock(mm); 111 if (pinned_pages <= 0) 112 return -EFAULT; 113 114 bytes = pinned_pages * PAGE_SIZE - start_offset; 115 if (bytes > len) 116 bytes = len; 117 118 rc = process_vm_rw_pages(process_pages, 119 start_offset, bytes, iter, 120 vm_write); 121 len -= bytes; 122 start_offset = 0; 123 nr_pages -= pinned_pages; 124 pa += pinned_pages * PAGE_SIZE; 125 126 /* If vm_write is set, the pages need to be made dirty: */ 127 unpin_user_pages_dirty_lock(process_pages, pinned_pages, 128 vm_write); 129 } 130 131 return rc; 132 } 133 134 /* Maximum number of entries for process pages array 135 which lives on stack */ 136 #define PVM_MAX_PP_ARRAY_COUNT 16 137 138 /** 139 * process_vm_rw_core - core of reading/writing pages from task specified 140 * @pid: PID of process to read/write from/to 141 * @iter: where to copy to/from locally 142 * @rvec: iovec array specifying where to copy to/from in the other process 143 * @riovcnt: size of rvec array 144 * @flags: currently unused 145 * @vm_write: 0 if reading from other process, 1 if writing to other process 146 * 147 * Returns the number of bytes read/written or error code. May 148 * return less bytes than expected if an error occurs during the copying 149 * process. 150 */ 151 static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, 152 const struct iovec *rvec, 153 unsigned long riovcnt, 154 unsigned long flags, int vm_write) 155 { 156 struct task_struct *task; 157 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; 158 struct page **process_pages = pp_stack; 159 struct mm_struct *mm; 160 unsigned long i; 161 ssize_t rc = 0; 162 unsigned long nr_pages = 0; 163 unsigned long nr_pages_iov; 164 ssize_t iov_len; 165 size_t total_len = iov_iter_count(iter); 166 167 /* 168 * Work out how many pages of struct pages we're going to need 169 * when eventually calling get_user_pages 170 */ 171 for (i = 0; i < riovcnt; i++) { 172 iov_len = rvec[i].iov_len; 173 if (iov_len > 0) { 174 nr_pages_iov = ((unsigned long)rvec[i].iov_base 175 + iov_len - 1) 176 / PAGE_SIZE - (unsigned long)rvec[i].iov_base 177 / PAGE_SIZE + 1; 178 nr_pages = max(nr_pages, nr_pages_iov); 179 } 180 } 181 182 if (nr_pages == 0) 183 return 0; 184 185 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { 186 /* For reliability don't try to kmalloc more than 187 2 pages worth */ 188 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES * PAGE_SIZE, 189 sizeof(struct page *)*nr_pages), 190 GFP_KERNEL); 191 192 if (!process_pages) 193 return -ENOMEM; 194 } 195 196 /* Get process information */ 197 task = find_get_task_by_vpid(pid); 198 if (!task) { 199 rc = -ESRCH; 200 goto free_proc_pages; 201 } 202 203 mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); 204 if (!mm || IS_ERR(mm)) { 205 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; 206 /* 207 * Explicitly map EACCES to EPERM as EPERM is a more 208 * appropriate error code for process_vw_readv/writev 209 */ 210 if (rc == -EACCES) 211 rc = -EPERM; 212 goto put_task_struct; 213 } 214 215 for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++) 216 rc = process_vm_rw_single_vec( 217 (unsigned long)rvec[i].iov_base, rvec[i].iov_len, 218 iter, process_pages, mm, task, vm_write); 219 220 /* copied = space before - space after */ 221 total_len -= iov_iter_count(iter); 222 223 /* If we have managed to copy any data at all then 224 we return the number of bytes copied. Otherwise 225 we return the error code */ 226 if (total_len) 227 rc = total_len; 228 229 mmput(mm); 230 231 put_task_struct: 232 put_task_struct(task); 233 234 free_proc_pages: 235 if (process_pages != pp_stack) 236 kfree(process_pages); 237 return rc; 238 } 239 240 /** 241 * process_vm_rw - check iovecs before calling core routine 242 * @pid: PID of process to read/write from/to 243 * @lvec: iovec array specifying where to copy to/from locally 244 * @liovcnt: size of lvec array 245 * @rvec: iovec array specifying where to copy to/from in the other process 246 * @riovcnt: size of rvec array 247 * @flags: currently unused 248 * @vm_write: 0 if reading from other process, 1 if writing to other process 249 * 250 * Returns the number of bytes read/written or error code. May 251 * return less bytes than expected if an error occurs during the copying 252 * process. 253 */ 254 static ssize_t process_vm_rw(pid_t pid, 255 const struct iovec __user *lvec, 256 unsigned long liovcnt, 257 const struct iovec __user *rvec, 258 unsigned long riovcnt, 259 unsigned long flags, int vm_write) 260 { 261 struct iovec iovstack_l[UIO_FASTIOV]; 262 struct iovec iovstack_r[UIO_FASTIOV]; 263 struct iovec *iov_l = iovstack_l; 264 struct iovec *iov_r; 265 struct iov_iter iter; 266 ssize_t rc; 267 int dir = vm_write ? ITER_SOURCE : ITER_DEST; 268 269 if (flags != 0) 270 return -EINVAL; 271 272 /* Check iovecs */ 273 rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); 274 if (rc < 0) 275 return rc; 276 if (!iov_iter_count(&iter)) 277 goto free_iov_l; 278 iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, 279 in_compat_syscall()); 280 if (IS_ERR(iov_r)) { 281 rc = PTR_ERR(iov_r); 282 goto free_iov_l; 283 } 284 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); 285 if (iov_r != iovstack_r) 286 kfree(iov_r); 287 free_iov_l: 288 kfree(iov_l); 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