mm/process_vm_access.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * linux/mm/process_vm_access.c
  *
  * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
  */

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

 /**
  * process_vm_rw_pages - read/write pages from task specified
  * @pages: array of pointers to pages we want to copy
  * @offset: offset in page to start copying from/to
  * @len: number of bytes to copy
  * @iter: where to copy to/from locally
  * @vm_write: 0 means copy from, 1 means copy to
  * Returns 0 on success, error code otherwise
  */
 static int process_vm_rw_pages(struct page **pages,
 			       unsigned offset,
 			       size_t len,
 			       struct iov_iter *iter,
 			       int vm_write)
 {
 	/* Do the copy for each page */
 	while (len && iov_iter_count(iter)) {
 		struct page *page = *pages++;
 		size_t copy = PAGE_SIZE - offset;
 		size_t copied;

 		if (copy > len)
 			copy = len;

 		if (vm_write)
 			copied = copy_page_from_iter(page, offset, copy, iter);
 		else
 			copied = copy_page_to_iter(page, offset, copy, iter);

 		len -= copied;
 		if (copied < copy && iov_iter_count(iter))
 			return -EFAULT;
 		offset = 0;
 	}
 	return 0;
 }

 /* 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
  * @iter: where to copy to/from locally
  * @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
  * Returns 0 on success or on failure error code
  */
 static int process_vm_rw_single_vec(unsigned long addr,
 				    unsigned long len,
 				    struct iov_iter *iter,
 				    struct page **process_pages,
 				    struct mm_struct *mm,
 				    struct task_struct *task,
 				    int vm_write)
 {
 	unsigned long pa = addr & PAGE_MASK;
 	unsigned long start_offset = addr - pa;
 	unsigned long nr_pages;
 	ssize_t rc = 0;
 	unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
 		/ sizeof(struct pages *);
 	unsigned int flags = 0;

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

 	if (vm_write)
 		flags |= FOLL_WRITE;

 	while (!rc && nr_pages && iov_iter_count(iter)) {
 		int pinned_pages = min(nr_pages, max_pages_per_loop);
 		int locked = 1;
 		size_t bytes;

 		/*
 		 * Get the pages we're interested in.  We must
 		 * access remotely because task/mm might not
 		 * current/current->mm
 		 */
 		mmap_read_lock(mm);
 		pinned_pages = pin_user_pages_remote(mm, pa, pinned_pages,
 						     flags, process_pages,
 						     NULL, &locked);
 		if (locked)
 			mmap_read_unlock(mm);
 		if (pinned_pages <= 0)
 			return -EFAULT;

 		bytes = pinned_pages * PAGE_SIZE - start_offset;
 		if (bytes > len)
 			bytes = len;

 		rc = process_vm_rw_pages(process_pages,
 					 start_offset, bytes, iter,
 					 vm_write);
 		len -= bytes;
 		start_offset = 0;
 		nr_pages -= pinned_pages;
 		pa += pinned_pages * PAGE_SIZE;

 		/* If vm_write is set, the pages need to be made dirty: */
 		unpin_user_pages_dirty_lock(process_pages, pinned_pages,
 					    vm_write);
 	}

 	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
  * @iter: where to copy to/from locally
  * @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_core(pid_t pid, struct iov_iter *iter,
 				  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;
 	unsigned long nr_pages = 0;
 	unsigned long nr_pages_iov;
 	ssize_t iov_len;
 	size_t total_len = iov_iter_count(iter);

 	/*
 	 * 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 */
 	task = find_get_task_by_vpid(pid);
 	if (!task) {
 		rc = -ESRCH;
 		goto free_proc_pages;
 	}

 	mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS);
 	if (!mm || IS_ERR(mm)) {
 		rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
 		/*
 		 * Explicitly map EACCES to EPERM as EPERM is a more
 		 * appropriate error code for process_vw_readv/writev
 		 */
 		if (rc == -EACCES)
 			rc = -EPERM;
 		goto put_task_struct;
 	}

 	for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
 		rc = process_vm_rw_single_vec(
 			(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
 			iter, process_pages, mm, task, vm_write);

 	/* copied = space before - space after */
 	total_len -= iov_iter_count(iter);

 	/* 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 (total_len)
 		rc = total_len;

 	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;
 	struct iov_iter iter;
 	ssize_t rc;
 	int dir = vm_write ? WRITE : READ;

 	if (flags != 0)
 		return -EINVAL;

 	/* Check iovecs */
 	rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
 	if (rc < 0)
 		return rc;
 	if (!iov_iter_count(&iter))
 		goto free_iov_l;
 	iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, false);
 	if (IS_ERR(iov_r)) {
 		rc = PTR_ERR(iov_r);
 		goto free_iov_l;
 	}
 	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
 	if (iov_r != iovstack_r)
 		kfree(iov_r);
 free_iov_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);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* linux/mm/process_vm_access.c
	*
	* Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
	*/

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

	/**
	* process_vm_rw_pages - read/write pages from task specified
	* @pages: array of pointers to pages we want to copy
	* @offset: offset in page to start copying from/to
	* @len: number of bytes to copy
	* @iter: where to copy to/from locally
	* @vm_write: 0 means copy from, 1 means copy to
	* Returns 0 on success, error code otherwise
	*/
	static int process_vm_rw_pages(struct page **pages,
	unsigned offset,
	size_t len,
	struct iov_iter *iter,
	int vm_write)
	{
	/* Do the copy for each page */
	while (len && iov_iter_count(iter)) {
	struct page page = pages++;
	size_t copy = PAGE_SIZE - offset;
	size_t copied;

	if (copy > len)
	copy = len;

	if (vm_write)
	copied = copy_page_from_iter(page, offset, copy, iter);
	else
	copied = copy_page_to_iter(page, offset, copy, iter);

	len -= copied;
	if (copied < copy && iov_iter_count(iter))
	return -EFAULT;
	offset = 0;
	}
	return 0;
	}

	/* 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
	* @iter: where to copy to/from locally
	* @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
	* Returns 0 on success or on failure error code
	*/
	static int process_vm_rw_single_vec(unsigned long addr,
	unsigned long len,
	struct iov_iter *iter,
	struct page **process_pages,
	struct mm_struct *mm,
	struct task_struct *task,
	int vm_write)
	{
	unsigned long pa = addr & PAGE_MASK;
	unsigned long start_offset = addr - pa;
	unsigned long nr_pages;
	ssize_t rc = 0;
	unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
	/ sizeof(struct pages *);
	unsigned int flags = 0;

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

	if (vm_write)
	flags \|= FOLL_WRITE;

	while (!rc && nr_pages && iov_iter_count(iter)) {
	int pinned_pages = min(nr_pages, max_pages_per_loop);
	int locked = 1;
	size_t bytes;

	/*
	* Get the pages we're interested in. We must
	* access remotely because task/mm might not
	* current/current->mm
	*/
	mmap_read_lock(mm);
	pinned_pages = pin_user_pages_remote(mm, pa, pinned_pages,
	flags, process_pages,
	NULL, &locked);
	if (locked)
	mmap_read_unlock(mm);
	if (pinned_pages <= 0)
	return -EFAULT;

	bytes = pinned_pages * PAGE_SIZE - start_offset;
	if (bytes > len)
	bytes = len;

	rc = process_vm_rw_pages(process_pages,
	start_offset, bytes, iter,
	vm_write);
	len -= bytes;
	start_offset = 0;
	nr_pages -= pinned_pages;
	pa += pinned_pages * PAGE_SIZE;

	/* If vm_write is set, the pages need to be made dirty: */
	unpin_user_pages_dirty_lock(process_pages, pinned_pages,
	vm_write);
	}

	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
	* @iter: where to copy to/from locally
	* @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_core(pid_t pid, struct iov_iter *iter,
	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;
	unsigned long nr_pages = 0;
	unsigned long nr_pages_iov;
	ssize_t iov_len;
	size_t total_len = iov_iter_count(iter);

	/*
	* 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 */
	task = find_get_task_by_vpid(pid);
	if (!task) {
	rc = -ESRCH;
	goto free_proc_pages;
	}

	mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS);
	if (!mm \|\| IS_ERR(mm)) {
	rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
	/*
	* Explicitly map EACCES to EPERM as EPERM is a more
	* appropriate error code for process_vw_readv/writev
	*/
	if (rc == -EACCES)
	rc = -EPERM;
	goto put_task_struct;
	}

	for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
	rc = process_vm_rw_single_vec(
	(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
	iter, process_pages, mm, task, vm_write);

	/* copied = space before - space after */
	total_len -= iov_iter_count(iter);

	/* 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 (total_len)
	rc = total_len;

	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;
	struct iov_iter iter;
	ssize_t rc;
	int dir = vm_write ? WRITE : READ;

	if (flags != 0)
	return -EINVAL;

	/* Check iovecs */
	rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
	if (rc < 0)
	return rc;
	if (!iov_iter_count(&iter))
	goto free_iov_l;
	iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, false);
	if (IS_ERR(iov_r)) {
	rc = PTR_ERR(iov_r);
	goto free_iov_l;
	}
	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
	if (iov_r != iovstack_r)
	kfree(iov_r);
	free_iov_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);
	}