Fix: ctf_user_integer should not trigger page fault

[lttng-modules.git] / lib / ringbuffer / backend.h

diff --git a/lib/ringbuffer/backend.h b/lib/ringbuffer/backend.h
index b908ed06e92665e127bac42e19d57ffbb7ec9670..8f6d7d04d8a8ed76d86ed694c44e1864cc05d509 100644 (file)
--- a/lib/ringbuffer/backend.h
+++ b/lib/ringbuffer/backend.h
@@ -478,4 +478,29 @@ unsigned long lib_ring_buffer_get_records_unread(
        return records_unread;
 }
 
+/*
+ * We use __copy_from_user_inatomic to copy userspace data after
+ * checking with access_ok() and disabling page faults.
+ *
+ * Return 0 if OK, nonzero on error.
+ */
+static inline
+unsigned long lib_ring_buffer_copy_from_user_check_nofault(void *dest,
+                                               const void __user *src,
+                                               unsigned long len)
+{
+       unsigned long ret;
+       mm_segment_t old_fs;
+
+       if (!access_ok(VERIFY_READ, src, len))
+               return 1;
+       old_fs = get_fs();
+       set_fs(KERNEL_DS);
+       pagefault_disable();
+       ret = __copy_from_user_inatomic(dest, src, len);
+       pagefault_enable();
+       set_fs(old_fs);
+       return ret;
+}
+
 #endif /* _LIB_RING_BUFFER_BACKEND_H */