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-rw-r--r--mm/process_vm_access.c305
1 files changed, 305 insertions, 0 deletions
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
new file mode 100644
index 000000000..c90d722c6
--- /dev/null
+++ b/mm/process_vm_access.c
@@ -0,0 +1,305 @@
+// 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/compat.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 (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 pinned_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
+ */
+ mmap_read_lock(mm);
+ pinned_pages = pin_user_pages_remote(mm, pa, pinned_pages,
+ flags, process_pages,
+ NULL, &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)
+ / 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
+ * 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_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);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-11 14:05:15 +0000