/* * 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, const struct iovec *lvec, unsigned long lvec_cnt, unsigned long *lvec_current, size_t *lvec_offset, 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; *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) && (*lvec_current < lvec_cnt); pgs_copied++) { /* Make sure we have a non zero length iovec */ while (*lvec_current < lvec_cnt && lvec[*lvec_current].iov_len == 0) (*lvec_current)++; if (*lvec_current == lvec_cnt) 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, lvec[*lvec_current].iov_len - *lvec_offset); target_kaddr = kmap(process_pages[pgs_copied]) + start_offset; if (vm_write) ret = copy_from_user(target_kaddr, lvec[*lvec_current].iov_base + *lvec_offset, bytes_to_copy); else ret = copy_to_user(lvec[*lvec_current].iov_base + *lvec_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; *lvec_offset += bytes_to_copy; if (*lvec_offset == lvec[*lvec_current].iov_len) { /* * Need to copy remaining part of page into the * next iovec if there are any bytes left in page */ (*lvec_current)++; *lvec_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]); } 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, const struct iovec *lvec, unsigned long lvec_cnt, unsigned long *lvec_current, size_t *lvec_offset, 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) && (*lvec_current < lvec_cnt)) { 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, lvec, lvec_cnt, lvec_current, lvec_offset, 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, const struct iovec *lvec, unsigned long liovcnt, 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; unsigned long iov_l_curr_idx = 0; size_t iov_l_curr_offset = 0; 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 && iov_l_curr_idx < liovcnt; i++) { rc = process_vm_rw_single_vec( (unsigned long)rvec[i].iov_base, rvec[i].iov_len, lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset, 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; 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, 1); else rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV, iovstack_l, &iov_l, 1); if (rc <= 0) goto free_iovecs; rc = rw_copy_check_uvector(READ, rvec, riovcnt, UIO_FASTIOV, iovstack_r, &iov_r, 0); if (rc <= 0) goto free_iovecs; rc = process_vm_rw_core(pid, iov_l, liovcnt, 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; ssize_t rc = -EFAULT; if (flags != 0) return -EINVAL; if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec))) goto out; if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec))) goto out; if (vm_write) rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV, iovstack_l, &iov_l, 1); else rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV, iovstack_l, &iov_l, 1); if (rc <= 0) goto free_iovecs; rc = compat_rw_copy_check_uvector(READ, rvec, riovcnt, UIO_FASTIOV, iovstack_r, &iov_r, 0); if (rc <= 0) goto free_iovecs; rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags, vm_write); free_iovecs: if (iov_r != iovstack_r) kfree(iov_r); if (iov_l != iovstack_l) kfree(iov_l); out: 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