[mirror_ubuntu-bionic-kernel.git] / mm / process_vm_access.c

/*
 * 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
 */
static int process_vm_rw_pages(struct task_struct *task,
			       struct mm_struct *mm,
			       struct page **process_pages,
			       unsigned long pa,
			       unsigned long start_offset,
			       unsigned long len,
			       struct iov_iter *iter,
			       int vm_write,
			       unsigned int nr_pages_to_copy,
			       ssize_t *bytes_copied)
{
	int pages_pinned;
	void *target_kaddr;
	int pgs_copied = 0;
	int j;
	int ret;
	ssize_t bytes_to_copy;
	ssize_t rc = 0;
	const struct iovec *iov = iter->iov;

	*bytes_copied = 0;

	/* 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 != nr_pages_to_copy) {
		rc = -EFAULT;
		goto end;
	}

	/* Do the copy for each page */
	for (pgs_copied = 0;
	     (pgs_copied < nr_pages_to_copy) && iter->nr_segs;
	     pgs_copied++) {
		/* Make sure we have a non zero length iovec */
		while (iter->nr_segs && iov->iov_len == 0) {
			iov++;
			iter->nr_segs--;
		}
		if (!iter->nr_segs)
			break;

		/*
		 * Will copy smallest of:
		 * - bytes remaining in page
		 * - bytes remaining in destination iovec
		 */
		bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
				      len - *bytes_copied);
		bytes_to_copy = min_t(ssize_t, bytes_to_copy,
				      iov->iov_len
				      - iter->iov_offset);

		target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;

		if (vm_write)
			ret = copy_from_user(target_kaddr,
					     iov->iov_base
					     + iter->iov_offset,
					     bytes_to_copy);
		else
			ret = copy_to_user(iov->iov_base
					   + iter->iov_offset,
					   target_kaddr, bytes_to_copy);
		kunmap(process_pages[pgs_copied]);
		if (ret) {
			*bytes_copied += bytes_to_copy - ret;
			pgs_copied++;
			rc = -EFAULT;
			goto end;
		}
		*bytes_copied += bytes_to_copy;
		iter->iov_offset += bytes_to_copy;
		if (iter->iov_offset == iov->iov_len) {
			/*
			 * Need to copy remaining part of page into the
			 * next iovec if there are any bytes left in page
			 */
			iter->nr_segs--;
			iov++;
			iter->iov_offset = 0;
			start_offset = (start_offset + bytes_to_copy)
				% PAGE_SIZE;
			if (start_offset)
				pgs_copied--;
		} else {
			start_offset = 0;
		}
	}

end:
	if (vm_write) {
		for (j = 0; j < pages_pinned; j++) {
			if (j < pgs_copied)
				set_page_dirty_lock(process_pages[j]);
			put_page(process_pages[j]);
		}
	} else {
		for (j = 0; j < pages_pinned; j++)
			put_page(process_pages[j]);
	}

	iter->iov = iov;
	return rc;
}

/* 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,
				    struct iov_iter *iter,
				    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 nr_pages_to_copy;
	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;

	while ((nr_pages_copied < nr_pages) && iter->nr_segs) {
		nr_pages_to_copy = min(nr_pages - nr_pages_copied,
				       max_pages_per_loop);

		rc = process_vm_rw_pages(task, mm, process_pages, pa,
					 start_offset, len, iter,
					 vm_write, nr_pages_to_copy,
					 &bytes_copied_loop);
		start_offset = 0;
		*bytes_copied += bytes_copied_loop;

		if (rc < 0) {
			return rc;
		} else {
			len -= bytes_copied_loop;
			nr_pages_copied += nr_pages_to_copy;
			pa += nr_pages_to_copy * PAGE_SIZE;
		}
	}

	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.
 */
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;
	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;
	}

	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;
		goto put_task_struct;
	}

	for (i = 0; i < riovcnt && iter->nr_segs; i++) {
		rc = process_vm_rw_single_vec(
			(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
			iter, process_pages, mm, task, vm_write,
			&bytes_copied_loop);
		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;
	struct iov_iter iter;
	ssize_t rc;

	if (flags != 0)
		return -EINVAL;

	/* Check iovecs */
	if (vm_write)
		rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
					   iovstack_l, &iov_l);
	else
		rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
					   iovstack_l, &iov_l);
	if (rc <= 0)
		goto free_iovecs;

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

	rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
				   iovstack_r, &iov_r);
	if (rc <= 0)
		goto free_iovecs;

	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);

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;
	struct iov_iter iter;
	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,
						  &iov_l);
	else
		rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
						  UIO_FASTIOV, iovstack_l,
						  &iov_l);
	if (rc <= 0)
		goto free_iovecs;
	iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
	rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
					  UIO_FASTIOV, iovstack_r,
					  &iov_r);
	if (rc <= 0)
		goto free_iovecs;

	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);

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
Commit	Line	Data
fcf63409 CY	1	/*
	2	* linux/mm/process_vm_access.c
	3	*
	4	* Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the License, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/mm.h>
	13	#include <linux/uio.h>
	14	#include <linux/sched.h>
	15	#include <linux/highmem.h>
	16	#include <linux/ptrace.h>
	17	#include <linux/slab.h>
	18	#include <linux/syscalls.h>
	19
	20	#ifdef CONFIG_COMPAT
	21	#include <linux/compat.h>
	22	#endif
	23
	24	/**
	25	* process_vm_rw_pages - read/write pages from task specified
	26	* @task: task to read/write from
	27	* @mm: mm for task
	28	* @process_pages: struct pages area that can store at least
	29	* nr_pages_to_copy struct page pointers
	30	* @pa: address of page in task to start copying from/to
	31	* @start_offset: offset in page to start copying from/to
	32	* @len: number of bytes to copy
	33	* @lvec: iovec array specifying where to copy to/from
	34	* @lvec_cnt: number of elements in iovec array
	35	* @lvec_current: index in iovec array we are up to
	36	* @lvec_offset: offset in bytes from current iovec iov_base we are up to
	37	* @vm_write: 0 means copy from, 1 means copy to
	38	* @nr_pages_to_copy: number of pages to copy
	39	* @bytes_copied: returns number of bytes successfully copied
	40	* Returns 0 on success, error code otherwise
	41	*/
	42	static int process_vm_rw_pages(struct task_struct *task,
	43	struct mm_struct *mm,
	44	struct page **process_pages,
	45	unsigned long pa,
	46	unsigned long start_offset,
	47	unsigned long len,
9f78bdfa	48	struct iov_iter *iter,
fcf63409 CY	49	int vm_write,
	50	unsigned int nr_pages_to_copy,
	51	ssize_t *bytes_copied)
	52	{
	53	int pages_pinned;
	54	void *target_kaddr;
	55	int pgs_copied = 0;
	56	int j;
	57	int ret;
	58	ssize_t bytes_to_copy;
	59	ssize_t rc = 0;
9f78bdfa	60	const struct iovec *iov = iter->iov;
fcf63409 CY	61
	62	*bytes_copied = 0;
	63
	64	/* Get the pages we're interested in */
	65	down_read(&mm->mmap_sem);
	66	pages_pinned = get_user_pages(task, mm, pa,
	67	nr_pages_to_copy,
	68	vm_write, 0, process_pages, NULL);
	69	up_read(&mm->mmap_sem);
	70
	71	if (pages_pinned != nr_pages_to_copy) {
	72	rc = -EFAULT;
	73	goto end;
	74	}
	75
	76	/* Do the copy for each page */
	77	for (pgs_copied = 0;
9f78bdfa	78	(pgs_copied < nr_pages_to_copy) && iter->nr_segs;
fcf63409 CY	79	pgs_copied++) {
fcf63409 CY	80	/* Make sure we have a non zero length iovec */
9f78bdfa	81	while (iter->nr_segs && iov->iov_len == 0) {
480402e1	82	iov++;
9f78bdfa	83	iter->nr_segs--;
480402e1	84	}
9f78bdfa	85	if (!iter->nr_segs)
fcf63409 CY	86	break;
	87
	88	/*
	89	* Will copy smallest of:
	90	* - bytes remaining in page
	91	* - bytes remaining in destination iovec
	92	*/
	93	bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
	94	len - *bytes_copied);
	95	bytes_to_copy = min_t(ssize_t, bytes_to_copy,
480402e1	96	iov->iov_len
9f78bdfa	97	- iter->iov_offset);
fcf63409 CY	98
	99	target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;
	100
	101	if (vm_write)
	102	ret = copy_from_user(target_kaddr,
480402e1	103	iov->iov_base
9f78bdfa	104	+ iter->iov_offset,
fcf63409 CY	105	bytes_to_copy);
fcf63409 CY	106	else
480402e1	107	ret = copy_to_user(iov->iov_base
9f78bdfa	108	+ iter->iov_offset,
fcf63409 CY	109	target_kaddr, bytes_to_copy);
	110	kunmap(process_pages[pgs_copied]);
	111	if (ret) {
	112	*bytes_copied += bytes_to_copy - ret;
	113	pgs_copied++;
	114	rc = -EFAULT;
	115	goto end;
	116	}
	117	*bytes_copied += bytes_to_copy;
9f78bdfa AV	118	iter->iov_offset += bytes_to_copy;
9f78bdfa AV	119	if (iter->iov_offset == iov->iov_len) {
fcf63409 CY	120	/*
	121	* Need to copy remaining part of page into the
	122	* next iovec if there are any bytes left in page
	123	*/
9f78bdfa	124	iter->nr_segs--;
480402e1	125	iov++;
9f78bdfa	126	iter->iov_offset = 0;
fcf63409 CY	127	start_offset = (start_offset + bytes_to_copy)
	128	% PAGE_SIZE;
	129	if (start_offset)
	130	pgs_copied--;
	131	} else {
	132	start_offset = 0;
	133	}
	134	}
	135
	136	end:
	137	if (vm_write) {
	138	for (j = 0; j < pages_pinned; j++) {
	139	if (j < pgs_copied)
	140	set_page_dirty_lock(process_pages[j]);
	141	put_page(process_pages[j]);
	142	}
	143	} else {
	144	for (j = 0; j < pages_pinned; j++)
	145	put_page(process_pages[j]);
	146	}
	147
9f78bdfa	148	iter->iov = iov;
fcf63409 CY	149	return rc;
	150	}
	151
	152	/* Maximum number of pages kmalloc'd to hold struct page's during copy */
	153	#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
	154
	155	/**
	156	* process_vm_rw_single_vec - read/write pages from task specified
	157	* @addr: start memory address of target process
	158	* @len: size of area to copy to/from
	159	* @lvec: iovec array specifying where to copy to/from locally
	160	* @lvec_cnt: number of elements in iovec array
	161	* @lvec_current: index in iovec array we are up to
	162	* @lvec_offset: offset in bytes from current iovec iov_base we are up to
	163	* @process_pages: struct pages area that can store at least
	164	* nr_pages_to_copy struct page pointers
	165	* @mm: mm for task
	166	* @task: task to read/write from
	167	* @vm_write: 0 means copy from, 1 means copy to
	168	* @bytes_copied: returns number of bytes successfully copied
	169	* Returns 0 on success or on failure error code
	170	*/
	171	static int process_vm_rw_single_vec(unsigned long addr,
	172	unsigned long len,
9f78bdfa	173	struct iov_iter *iter,
fcf63409 CY	174	struct page **process_pages,
	175	struct mm_struct *mm,
	176	struct task_struct *task,
	177	int vm_write,
	178	ssize_t *bytes_copied)
	179	{
	180	unsigned long pa = addr & PAGE_MASK;
	181	unsigned long start_offset = addr - pa;
	182	unsigned long nr_pages;
	183	ssize_t bytes_copied_loop;
	184	ssize_t rc = 0;
	185	unsigned long nr_pages_copied = 0;
	186	unsigned long nr_pages_to_copy;
	187	unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
	188	/ sizeof(struct pages *);
	189
	190	*bytes_copied = 0;
	191
	192	/* Work out address and page range required */
	193	if (len == 0)
	194	return 0;
	195	nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
	196
9f78bdfa	197	while ((nr_pages_copied < nr_pages) && iter->nr_segs) {
fcf63409 CY	198	nr_pages_to_copy = min(nr_pages - nr_pages_copied,
	199	max_pages_per_loop);
	200
	201	rc = process_vm_rw_pages(task, mm, process_pages, pa,
9f78bdfa	202	start_offset, len, iter,
fcf63409 CY	203	vm_write, nr_pages_to_copy,
	204	&bytes_copied_loop);
	205	start_offset = 0;
	206	*bytes_copied += bytes_copied_loop;
	207
	208	if (rc < 0) {
	209	return rc;
	210	} else {
	211	len -= bytes_copied_loop;
	212	nr_pages_copied += nr_pages_to_copy;
	213	pa += nr_pages_to_copy * PAGE_SIZE;
	214	}
	215	}
	216
	217	return rc;
	218	}
	219
	220	/* Maximum number of entries for process pages array
	221	which lives on stack */
	222	#define PVM_MAX_PP_ARRAY_COUNT 16
	223
	224	/**
	225	* process_vm_rw_core - core of reading/writing pages from task specified
	226	* @pid: PID of process to read/write from/to
	227	* @lvec: iovec array specifying where to copy to/from locally
	228	* @liovcnt: size of lvec array
	229	* @rvec: iovec array specifying where to copy to/from in the other process
	230	* @riovcnt: size of rvec array
	231	* @flags: currently unused
	232	* @vm_write: 0 if reading from other process, 1 if writing to other process
	233	* Returns the number of bytes read/written or error code. May
	234	* return less bytes than expected if an error occurs during the copying
	235	* process.
	236	*/
9f78bdfa	237	static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
fcf63409 CY	238	const struct iovec *rvec,
	239	unsigned long riovcnt,
	240	unsigned long flags, int vm_write)
	241	{
	242	struct task_struct *task;
	243	struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
	244	struct page **process_pages = pp_stack;
	245	struct mm_struct *mm;
	246	unsigned long i;
	247	ssize_t rc = 0;
	248	ssize_t bytes_copied_loop;
	249	ssize_t bytes_copied = 0;
	250	unsigned long nr_pages = 0;
	251	unsigned long nr_pages_iov;
fcf63409 CY	252	ssize_t iov_len;
	253
	254	/*
	255	* Work out how many pages of struct pages we're going to need
	256	* when eventually calling get_user_pages
	257	*/
	258	for (i = 0; i < riovcnt; i++) {
	259	iov_len = rvec[i].iov_len;
	260	if (iov_len > 0) {
	261	nr_pages_iov = ((unsigned long)rvec[i].iov_base
	262	+ iov_len)
	263	/ PAGE_SIZE - (unsigned long)rvec[i].iov_base
	264	/ PAGE_SIZE + 1;
	265	nr_pages = max(nr_pages, nr_pages_iov);
	266	}
	267	}
	268
	269	if (nr_pages == 0)
	270	return 0;
	271
	272	if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
	273	/* For reliability don't try to kmalloc more than
	274	2 pages worth */
	275	process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
	276	sizeof(struct pages )nr_pages),
	277	GFP_KERNEL);
	278
	279	if (!process_pages)
	280	return -ENOMEM;
	281	}
	282
	283	/* Get process information */
	284	rcu_read_lock();
	285	task = find_task_by_vpid(pid);
	286	if (task)
	287	get_task_struct(task);
	288	rcu_read_unlock();
	289	if (!task) {
	290	rc = -ESRCH;
	291	goto free_proc_pages;
	292	}
	293
8cdb878d CY	294	mm = mm_access(task, PTRACE_MODE_ATTACH);
	295	if (!mm \|\| IS_ERR(mm)) {
	296	rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
	297	/*
	298	* Explicitly map EACCES to EPERM as EPERM is a more a
	299	* appropriate error code for process_vw_readv/writev
	300	*/
	301	if (rc == -EACCES)
	302	rc = -EPERM;
fcf63409 CY	303	goto put_task_struct;
	304	}
	305
9f78bdfa	306	for (i = 0; i < riovcnt && iter->nr_segs; i++) {
fcf63409 CY	307	rc = process_vm_rw_single_vec(
fcf63409 CY	308	(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
9f78bdfa AV	309	iter, process_pages, mm, task, vm_write,
9f78bdfa AV	310	&bytes_copied_loop);
fcf63409 CY	311	bytes_copied += bytes_copied_loop;
	312	if (rc != 0) {
	313	/* If we have managed to copy any data at all then
	314	we return the number of bytes copied. Otherwise
	315	we return the error code */
	316	if (bytes_copied)
	317	rc = bytes_copied;
	318	goto put_mm;
	319	}
	320	}
	321
	322	rc = bytes_copied;
	323	put_mm:
	324	mmput(mm);
	325
	326	put_task_struct:
	327	put_task_struct(task);
	328
	329	free_proc_pages:
	330	if (process_pages != pp_stack)
	331	kfree(process_pages);
	332	return rc;
	333	}
	334
	335	/**
	336	* process_vm_rw - check iovecs before calling core routine
	337	* @pid: PID of process to read/write from/to
	338	* @lvec: iovec array specifying where to copy to/from locally
	339	* @liovcnt: size of lvec array
	340	* @rvec: iovec array specifying where to copy to/from in the other process
	341	* @riovcnt: size of rvec array
	342	* @flags: currently unused
	343	* @vm_write: 0 if reading from other process, 1 if writing to other process
	344	* Returns the number of bytes read/written or error code. May
	345	* return less bytes than expected if an error occurs during the copying
	346	* process.
	347	*/
	348	static ssize_t process_vm_rw(pid_t pid,
	349	const struct iovec __user *lvec,
	350	unsigned long liovcnt,
	351	const struct iovec __user *rvec,
	352	unsigned long riovcnt,
	353	unsigned long flags, int vm_write)
	354	{
	355	struct iovec iovstack_l[UIO_FASTIOV];
	356	struct iovec iovstack_r[UIO_FASTIOV];
	357	struct iovec *iov_l = iovstack_l;
	358	struct iovec *iov_r = iovstack_r;
9f78bdfa	359	struct iov_iter iter;
fcf63409 CY	360	ssize_t rc;
	361
	362	if (flags != 0)
	363	return -EINVAL;
	364
	365	/* Check iovecs */
	366	if (vm_write)
	367	rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
ac34ebb3	368	iovstack_l, &iov_l);
fcf63409 CY	369	else
fcf63409 CY	370	rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
ac34ebb3	371	iovstack_l, &iov_l);
fcf63409 CY	372	if (rc <= 0)
	373	goto free_iovecs;
	374
9f78bdfa AV	375	iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
9f78bdfa AV	376
ac34ebb3 CY	377	rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
ac34ebb3 CY	378	iovstack_r, &iov_r);
fcf63409 CY	379	if (rc <= 0)
	380	goto free_iovecs;
	381
9f78bdfa	382	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
fcf63409 CY	383
	384	free_iovecs:
	385	if (iov_r != iovstack_r)
	386	kfree(iov_r);
	387	if (iov_l != iovstack_l)
	388	kfree(iov_l);
	389
	390	return rc;
	391	}
	392
	393	SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
	394	unsigned long, liovcnt, const struct iovec __user *, rvec,
	395	unsigned long, riovcnt, unsigned long, flags)
	396	{
	397	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
	398	}
	399
	400	SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
	401	const struct iovec __user *, lvec,
	402	unsigned long, liovcnt, const struct iovec __user *, rvec,
	403	unsigned long, riovcnt, unsigned long, flags)
	404	{
	405	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
	406	}
	407
	408	#ifdef CONFIG_COMPAT
	409
	410	asmlinkage ssize_t
	411	compat_process_vm_rw(compat_pid_t pid,
	412	const struct compat_iovec __user *lvec,
	413	unsigned long liovcnt,
	414	const struct compat_iovec __user *rvec,
	415	unsigned long riovcnt,
	416	unsigned long flags, int vm_write)
	417	{
	418	struct iovec iovstack_l[UIO_FASTIOV];
	419	struct iovec iovstack_r[UIO_FASTIOV];
	420	struct iovec *iov_l = iovstack_l;
	421	struct iovec *iov_r = iovstack_r;
9f78bdfa	422	struct iov_iter iter;
fcf63409 CY	423	ssize_t rc = -EFAULT;
	424
	425	if (flags != 0)
	426	return -EINVAL;
	427
fcf63409 CY	428	if (vm_write)
	429	rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
	430	UIO_FASTIOV, iovstack_l,
ac34ebb3	431	&iov_l);
fcf63409 CY	432	else
	433	rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
	434	UIO_FASTIOV, iovstack_l,
ac34ebb3	435	&iov_l);
fcf63409 CY	436	if (rc <= 0)
fcf63409 CY	437	goto free_iovecs;
9f78bdfa	438	iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
ac34ebb3	439	rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
fcf63409	440	UIO_FASTIOV, iovstack_r,
ac34ebb3	441	&iov_r);
fcf63409 CY	442	if (rc <= 0)
	443	goto free_iovecs;
	444
9f78bdfa	445	rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
fcf63409 CY	446
	447	free_iovecs:
	448	if (iov_r != iovstack_r)
	449	kfree(iov_r);
	450	if (iov_l != iovstack_l)
	451	kfree(iov_l);
fcf63409 CY	452	return rc;
	453	}
	454
	455	asmlinkage ssize_t
	456	compat_sys_process_vm_readv(compat_pid_t pid,
	457	const struct compat_iovec __user *lvec,
	458	unsigned long liovcnt,
	459	const struct compat_iovec __user *rvec,
	460	unsigned long riovcnt,
	461	unsigned long flags)
	462	{
	463	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
	464	riovcnt, flags, 0);
	465	}
	466
	467	asmlinkage ssize_t
	468	compat_sys_process_vm_writev(compat_pid_t pid,
	469	const struct compat_iovec __user *lvec,
	470	unsigned long liovcnt,
	471	const struct compat_iovec __user *rvec,
	472	unsigned long riovcnt,
	473	unsigned long flags)
	474	{
	475	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
	476	riovcnt, flags, 1);
	477	}
	478
	479	#endif