2 files changed, 498 insertions, 1 deletions

diff --git a/mm/Makefile b/mm/Makefile
index 836e4163c1bf..50ec00ef2a0e 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -5,7 +5,8 @@
 mmu-y                   := nommu.o
 mmu-$(CONFIG_MMU)       := fremap.o highmem.o madvise.o memory.o mincore.o \
                            mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
-                           vmalloc.o pagewalk.o pgtable-generic.o
+                           vmalloc.o pagewalk.o pgtable-generic.o \
+                           process_vm_access.o
 
 obj-y                   := filemap.o mempool.o oom_kill.o fadvise.o \
                            maccess.o page_alloc.o page-writeback.o \
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
new file mode 100644
index 000000000000..e920aa3ce104
--- /dev/null
+++ b/mm/process_vm_access.c
@@ -0,0 +1,496 @@
+/*
+ * 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;
+        }
+
+        task_lock(task);
+        if (__ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
+                task_unlock(task);
+                rc = -EPERM;
+                goto put_task_struct;
+        }
+        mm = task->mm;
+
+        if (!mm || (task->flags & PF_KTHREAD)) {
+                task_unlock(task);
+                rc = -EINVAL;
+                goto put_task_struct;
+        }
+
+        atomic_inc(&mm->mm_users);
+        task_unlock(task);
+
+        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