process_vm_access.c 11.5 KB
Newer Older
Christopher Yeoh's avatar
Christopher Yeoh committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41
/*
 * linux/mm/process_vm_access.c
 *
 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/mm.h>
#include <linux/uio.h>
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/syscalls.h>

#ifdef CONFIG_COMPAT
#include <linux/compat.h>
#endif

/**
 * process_vm_rw_pages - read/write pages from task specified
 * @task: task to read/write from
 * @mm: mm for task
 * @process_pages: struct pages area that can store at least
 *  nr_pages_to_copy struct page pointers
 * @pa: address of page in task to start copying from/to
 * @start_offset: offset in page to start copying from/to
 * @len: number of bytes to copy
 * @lvec: iovec array specifying where to copy to/from
 * @lvec_cnt: number of elements in iovec array
 * @lvec_current: index in iovec array we are up to
 * @lvec_offset: offset in bytes from current iovec iov_base we are up to
 * @vm_write: 0 means copy from, 1 means copy to
 * @nr_pages_to_copy: number of pages to copy
 * @bytes_copied: returns number of bytes successfully copied
 * Returns 0 on success, error code otherwise
 */
42 43
static int process_vm_rw_pages(struct page **pages,
			       unsigned offset,
44
			       size_t len,
45
			       struct iov_iter *iter,
Christopher Yeoh's avatar
Christopher Yeoh committed
46 47 48 49 50 51
			       int vm_write,
			       ssize_t *bytes_copied)
{
	*bytes_copied = 0;

	/* Do the copy for each page */
52
	while (iov_iter_count(iter) && len) {
53
		struct page *page = *pages++;
54
		size_t copy = PAGE_SIZE - offset;
55
		size_t copied;
56

57 58 59
		if (copy > len)
			copy = len;

60
		if (vm_write) {
61 62 63 64 65
			if (copy > iov_iter_count(iter))
				copy = iov_iter_count(iter);
			copied = iov_iter_copy_from_user(page, iter,
					offset, copy);
			iov_iter_advance(iter, copied);
66 67
			set_page_dirty_lock(page);
		} else {
68
			copied = copy_page_to_iter(page, offset, copy, iter);
Christopher Yeoh's avatar
Christopher Yeoh committed
69
		}
70 71 72 73 74
		*bytes_copied += copied;
		len -= copied;
		if (copied < copy && iov_iter_count(iter))
			return -EFAULT;
		offset = 0;
Christopher Yeoh's avatar
Christopher Yeoh committed
75
	}
76
	return 0;
Christopher Yeoh's avatar
Christopher Yeoh committed
77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
}

/* Maximum number of pages kmalloc'd to hold struct page's during copy */
#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)

/**
 * process_vm_rw_single_vec - read/write pages from task specified
 * @addr: start memory address of target process
 * @len: size of area to copy to/from
 * @lvec: iovec array specifying where to copy to/from locally
 * @lvec_cnt: number of elements in iovec array
 * @lvec_current: index in iovec array we are up to
 * @lvec_offset: offset in bytes from current iovec iov_base we are up to
 * @process_pages: struct pages area that can store at least
 *  nr_pages_to_copy struct page pointers
 * @mm: mm for task
 * @task: task to read/write from
 * @vm_write: 0 means copy from, 1 means copy to
 * @bytes_copied: returns number of bytes successfully copied
 * Returns 0 on success or on failure error code
 */
static int process_vm_rw_single_vec(unsigned long addr,
				    unsigned long len,
100
				    struct iov_iter *iter,
Christopher Yeoh's avatar
Christopher Yeoh committed
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122
				    struct page **process_pages,
				    struct mm_struct *mm,
				    struct task_struct *task,
				    int vm_write,
				    ssize_t *bytes_copied)
{
	unsigned long pa = addr & PAGE_MASK;
	unsigned long start_offset = addr - pa;
	unsigned long nr_pages;
	ssize_t bytes_copied_loop;
	ssize_t rc = 0;
	unsigned long nr_pages_copied = 0;
	unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
		/ sizeof(struct pages *);

	*bytes_copied = 0;

	/* Work out address and page range required */
	if (len == 0)
		return 0;
	nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;

123
	while ((nr_pages_copied < nr_pages) && iov_iter_count(iter)) {
124 125
		int nr_pages_to_copy;
		int pages_pinned;
126
		size_t n;
Christopher Yeoh's avatar
Christopher Yeoh committed
127 128 129
		nr_pages_to_copy = min(nr_pages - nr_pages_copied,
				       max_pages_per_loop);

130 131 132 133 134 135 136 137 138 139
		/* Get the pages we're interested in */
		down_read(&mm->mmap_sem);
		pages_pinned = get_user_pages(task, mm, pa,
					      nr_pages_to_copy,
					      vm_write, 0, process_pages, NULL);
		up_read(&mm->mmap_sem);

		if (pages_pinned <= 0)
			return -EFAULT;

140 141 142 143
		n = pages_pinned * PAGE_SIZE - start_offset;
		if (n > len)
			n = len;

144
		rc = process_vm_rw_pages(process_pages,
145 146
					 start_offset, n, iter,
					 vm_write,
Christopher Yeoh's avatar
Christopher Yeoh committed
147
					 &bytes_copied_loop);
148
		len -= n;
Christopher Yeoh's avatar
Christopher Yeoh committed
149 150
		start_offset = 0;
		*bytes_copied += bytes_copied_loop;
151 152 153 154 155 156
		nr_pages_copied += pages_pinned;
		pa += pages_pinned * PAGE_SIZE;
		while (pages_pinned)
			put_page(process_pages[--pages_pinned]);
		if (rc < 0)
			break;
Christopher Yeoh's avatar
Christopher Yeoh committed
157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178
	}

	return rc;
}

/* Maximum number of entries for process pages array
   which lives on stack */
#define PVM_MAX_PP_ARRAY_COUNT 16

/**
 * process_vm_rw_core - core of reading/writing pages from task specified
 * @pid: PID of process to read/write from/to
 * @lvec: iovec array specifying where to copy to/from locally
 * @liovcnt: size of lvec array
 * @rvec: iovec array specifying where to copy to/from in the other process
 * @riovcnt: size of rvec array
 * @flags: currently unused
 * @vm_write: 0 if reading from other process, 1 if writing to other process
 * Returns the number of bytes read/written or error code. May
 *  return less bytes than expected if an error occurs during the copying
 *  process.
 */
179
static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
Christopher Yeoh's avatar
Christopher Yeoh committed
180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235
				  const struct iovec *rvec,
				  unsigned long riovcnt,
				  unsigned long flags, int vm_write)
{
	struct task_struct *task;
	struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
	struct page **process_pages = pp_stack;
	struct mm_struct *mm;
	unsigned long i;
	ssize_t rc = 0;
	ssize_t bytes_copied_loop;
	ssize_t bytes_copied = 0;
	unsigned long nr_pages = 0;
	unsigned long nr_pages_iov;
	ssize_t iov_len;

	/*
	 * Work out how many pages of struct pages we're going to need
	 * when eventually calling get_user_pages
	 */
	for (i = 0; i < riovcnt; i++) {
		iov_len = rvec[i].iov_len;
		if (iov_len > 0) {
			nr_pages_iov = ((unsigned long)rvec[i].iov_base
					+ iov_len)
				/ PAGE_SIZE - (unsigned long)rvec[i].iov_base
				/ PAGE_SIZE + 1;
			nr_pages = max(nr_pages, nr_pages_iov);
		}
	}

	if (nr_pages == 0)
		return 0;

	if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
		/* For reliability don't try to kmalloc more than
		   2 pages worth */
		process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
					      sizeof(struct pages *)*nr_pages),
					GFP_KERNEL);

		if (!process_pages)
			return -ENOMEM;
	}

	/* Get process information */
	rcu_read_lock();
	task = find_task_by_vpid(pid);
	if (task)
		get_task_struct(task);
	rcu_read_unlock();
	if (!task) {
		rc = -ESRCH;
		goto free_proc_pages;
	}

236 237 238 239 240 241 242 243 244
	mm = mm_access(task, PTRACE_MODE_ATTACH);
	if (!mm || IS_ERR(mm)) {
		rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
		/*
		 * Explicitly map EACCES to EPERM as EPERM is a more a
		 * appropriate error code for process_vw_readv/writev
		 */
		if (rc == -EACCES)
			rc = -EPERM;
Christopher Yeoh's avatar
Christopher Yeoh committed
245 246 247
		goto put_task_struct;
	}

248
	for (i = 0; i < riovcnt && iov_iter_count(iter); i++) {
Christopher Yeoh's avatar
Christopher Yeoh committed
249 250
		rc = process_vm_rw_single_vec(
			(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
251 252
			iter, process_pages, mm, task, vm_write,
			&bytes_copied_loop);
Christopher Yeoh's avatar
Christopher Yeoh committed
253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300
		bytes_copied += bytes_copied_loop;
		if (rc != 0) {
			/* If we have managed to copy any data at all then
			   we return the number of bytes copied. Otherwise
			   we return the error code */
			if (bytes_copied)
				rc = bytes_copied;
			goto put_mm;
		}
	}

	rc = bytes_copied;
put_mm:
	mmput(mm);

put_task_struct:
	put_task_struct(task);

free_proc_pages:
	if (process_pages != pp_stack)
		kfree(process_pages);
	return rc;
}

/**
 * process_vm_rw - check iovecs before calling core routine
 * @pid: PID of process to read/write from/to
 * @lvec: iovec array specifying where to copy to/from locally
 * @liovcnt: size of lvec array
 * @rvec: iovec array specifying where to copy to/from in the other process
 * @riovcnt: size of rvec array
 * @flags: currently unused
 * @vm_write: 0 if reading from other process, 1 if writing to other process
 * Returns the number of bytes read/written or error code. May
 *  return less bytes than expected if an error occurs during the copying
 *  process.
 */
static ssize_t process_vm_rw(pid_t pid,
			     const struct iovec __user *lvec,
			     unsigned long liovcnt,
			     const struct iovec __user *rvec,
			     unsigned long riovcnt,
			     unsigned long flags, int vm_write)
{
	struct iovec iovstack_l[UIO_FASTIOV];
	struct iovec iovstack_r[UIO_FASTIOV];
	struct iovec *iov_l = iovstack_l;
	struct iovec *iov_r = iovstack_r;
301
	struct iov_iter iter;
Christopher Yeoh's avatar
Christopher Yeoh committed
302 303 304 305 306 307 308 309
	ssize_t rc;

	if (flags != 0)
		return -EINVAL;

	/* Check iovecs */
	if (vm_write)
		rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
310
					   iovstack_l, &iov_l);
Christopher Yeoh's avatar
Christopher Yeoh committed
311 312
	else
		rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
313
					   iovstack_l, &iov_l);
Christopher Yeoh's avatar
Christopher Yeoh committed
314 315 316
	if (rc <= 0)
		goto free_iovecs;

317 318
	iov_iter_init(&iter, iov_l, liovcnt, rc, 0);

319 320
	rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
				   iovstack_r, &iov_r);
Christopher Yeoh's avatar
Christopher Yeoh committed
321 322 323
	if (rc <= 0)
		goto free_iovecs;

324
	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
Christopher Yeoh's avatar
Christopher Yeoh committed
325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363

free_iovecs:
	if (iov_r != iovstack_r)
		kfree(iov_r);
	if (iov_l != iovstack_l)
		kfree(iov_l);

	return rc;
}

SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
		unsigned long, liovcnt, const struct iovec __user *, rvec,
		unsigned long, riovcnt,	unsigned long, flags)
{
	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
}

SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
		const struct iovec __user *, lvec,
		unsigned long, liovcnt, const struct iovec __user *, rvec,
		unsigned long, riovcnt,	unsigned long, flags)
{
	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
}

#ifdef CONFIG_COMPAT

asmlinkage ssize_t
compat_process_vm_rw(compat_pid_t pid,
		     const struct compat_iovec __user *lvec,
		     unsigned long liovcnt,
		     const struct compat_iovec __user *rvec,
		     unsigned long riovcnt,
		     unsigned long flags, int vm_write)
{
	struct iovec iovstack_l[UIO_FASTIOV];
	struct iovec iovstack_r[UIO_FASTIOV];
	struct iovec *iov_l = iovstack_l;
	struct iovec *iov_r = iovstack_r;
364
	struct iov_iter iter;
Christopher Yeoh's avatar
Christopher Yeoh committed
365 366 367 368 369 370 371 372
	ssize_t rc = -EFAULT;

	if (flags != 0)
		return -EINVAL;

	if (vm_write)
		rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
						  UIO_FASTIOV, iovstack_l,
373
						  &iov_l);
Christopher Yeoh's avatar
Christopher Yeoh committed
374 375 376
	else
		rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
						  UIO_FASTIOV, iovstack_l,
377
						  &iov_l);
Christopher Yeoh's avatar
Christopher Yeoh committed
378 379
	if (rc <= 0)
		goto free_iovecs;
380
	iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
381
	rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
Christopher Yeoh's avatar
Christopher Yeoh committed
382
					  UIO_FASTIOV, iovstack_r,
383
					  &iov_r);
Christopher Yeoh's avatar
Christopher Yeoh committed
384 385 386
	if (rc <= 0)
		goto free_iovecs;

387
	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
Christopher Yeoh's avatar
Christopher Yeoh committed
388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421

free_iovecs:
	if (iov_r != iovstack_r)
		kfree(iov_r);
	if (iov_l != iovstack_l)
		kfree(iov_l);
	return rc;
}

asmlinkage ssize_t
compat_sys_process_vm_readv(compat_pid_t pid,
			    const struct compat_iovec __user *lvec,
			    unsigned long liovcnt,
			    const struct compat_iovec __user *rvec,
			    unsigned long riovcnt,
			    unsigned long flags)
{
	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
				    riovcnt, flags, 0);
}

asmlinkage ssize_t
compat_sys_process_vm_writev(compat_pid_t pid,
			     const struct compat_iovec __user *lvec,
			     unsigned long liovcnt,
			     const struct compat_iovec __user *rvec,
			     unsigned long riovcnt,
			     unsigned long flags)
{
	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
				    riovcnt, flags, 1);
}

#endif