+ }
+ return 0;
+}
+
+/**
+ * replace_mm_exe_file - replace a reference to the mm's executable file
+ *
+ * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
+ * dealing with concurrent invocation and without grabbing the mmap lock in
+ * write mode.
+ *
+ * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
+ */
+int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
+{
+ struct vm_area_struct *vma;
+ struct file *old_exe_file;
+ int ret = 0;
+
+ /* Forbid mm->exe_file change if old file still mapped. */
+ old_exe_file = get_mm_exe_file(mm);
+ if (old_exe_file) {
+ mmap_read_lock(mm);
+ for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
+ if (!vma->vm_file)
+ continue;
+ if (path_equal(&vma->vm_file->f_path,
+ &old_exe_file->f_path))
+ ret = -EBUSY;
+ }
+ mmap_read_unlock(mm);
+ fput(old_exe_file);
+ if (ret)
+ return ret;
+ }
+
+ /* set the new file, lockless */
+ ret = deny_write_access(new_exe_file);
+ if (ret)
+ return -EACCES;
+ get_file(new_exe_file);
+
+ old_exe_file = xchg(&mm->exe_file, new_exe_file);
+ if (old_exe_file) {
+ /*
+ * Don't race with dup_mmap() getting the file and disallowing
+ * write access while someone might open the file writable.
+ */
+ mmap_read_lock(mm);
+ allow_write_access(old_exe_file);
+ fput(old_exe_file);
+ mmap_read_unlock(mm);
+ }
+ return 0;