// 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/compat.h>#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 2 /* Maximum number of pages that can be stored at a time */#define PVM_MAX_USER_PAGES (PVM_MAX_KMALLOC_PAGES * PAGE_SIZE / sizeof(struct page *)) /** * 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 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_t(unsigned long, nr_pages, PVM_MAX_USER_PAGES);		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,						     &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 - 1)				/ 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 * PAGE_SIZE,					      sizeof(struct page *)*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 (IS_ERR(mm)) {		rc = PTR_ERR(mm);		/*		 * 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;	struct iov_iter iter;	ssize_t rc;	int dir = vm_write ? ITER_SOURCE : ITER_DEST; 	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,				in_compat_syscall());	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);}