// SPDX-License-Identifier: GPL-2.0-or-later /* * linux/mm/process_vm_access.c * * Copyright (C) 2010-2011 Christopher Yeoh , IBM Corp. */ #include #include #include #include #include #include #include #include #include /** * 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); }