diff options
Diffstat (limited to 'mm/process_vm_access.c')
| -rw-r--r-- | mm/process_vm_access.c | 376 |
1 files changed, 376 insertions, 0 deletions
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c new file mode 100644 index 000000000..a447092d4 --- /dev/null +++ b/mm/process_vm_access.c @@ -0,0 +1,376 @@ +/* + * 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/sched/mm.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 + * @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); + set_page_dirty_lock(page); + } 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 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 + */ + down_read(&mm->mmap_sem); + pages = get_user_pages_remote(task, mm, pa, pages, flags, + process_pages, NULL, &locked); + if (locked) + up_read(&mm->mmap_sem); + if (pages <= 0) + return -EFAULT; + + bytes = 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 -= pages; + pa += pages * PAGE_SIZE; + while (pages) + put_page(process_pages[--pages]); + } + + 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 a + * 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_iovecs; + + 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); + 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 + +static 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; + int dir = vm_write ? WRITE : READ; + + if (flags != 0) + return -EINVAL; + + rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); + if (rc < 0) + return rc; + if (!iov_iter_count(&iter)) + goto free_iovecs; + 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); + kfree(iov_l); + return rc; +} + +COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid, + const struct compat_iovec __user *, lvec, + compat_ulong_t, liovcnt, + const struct compat_iovec __user *, rvec, + compat_ulong_t, riovcnt, + compat_ulong_t, flags) +{ + return compat_process_vm_rw(pid, lvec, liovcnt, rvec, + riovcnt, flags, 0); +} + +COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid, + const struct compat_iovec __user *, lvec, + compat_ulong_t, liovcnt, + const struct compat_iovec __user *, rvec, + compat_ulong_t, riovcnt, + compat_ulong_t, flags) +{ + return compat_process_vm_rw(pid, lvec, liovcnt, rvec, + riovcnt, flags, 1); +} + +#endif |