Fix use-after-free in record_btrace_start_replaying

-fsanitize=address showed a use-after-free in
record_btrace_start_replaying.  The bug occurred because
get_thread_current_frame returned a frame_info, but this object was
then invalidated before the return by ~scoped_restore_current_thread.

This patch fixes the problem by renaming get_thread_current_frame and
having it return a frame id.

gdb/ChangeLog
2018-10-23  Tom Tromey  <tom@tromey.com>

	* record-btrace.c (get_thread_current_frame_id): Rename from
	get_thread_current_frame.  Return a frame_id.
	(record_btrace_start_replaying): Update.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index db4c6b1..19a87f4 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2018-10-23  Tom Tromey  <tom@tromey.com>
+
+       * record-btrace.c (get_thread_current_frame_id): Rename from
+       get_thread_current_frame.  Return a frame_id.
+       (record_btrace_start_replaying): Update.
+
 2018-10-23  Andrew Burgess  <andrew.burgess@embecosm.com>
 
        * riscv-tdep.c (riscv_register_name): Use the user-friendly names

diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index aabe9f5..c0e3341 100644 (file)
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -1967,10 +1967,10 @@ record_btrace_resume_thread (struct thread_info *tp,
 
 /* Get the current frame for TP.  */
 
-static struct frame_info *
-get_thread_current_frame (struct thread_info *tp)
+static struct frame_id
+get_thread_current_frame_id (struct thread_info *tp)
 {
-  struct frame_info *frame;
+  struct frame_id id;
   int executing;
 
   /* Set current thread, which is implicitly used by
@@ -1989,10 +1989,10 @@ get_thread_current_frame (struct thread_info *tp)
   executing = tp->executing;
   set_executing (inferior_ptid, false);
 
-  frame = NULL;
+  id = null_frame_id;
   TRY
     {
-      frame = get_current_frame ();
+      id = get_frame_id (get_current_frame ());
     }
   CATCH (except, RETURN_MASK_ALL)
     {
@@ -2006,7 +2006,7 @@ get_thread_current_frame (struct thread_info *tp)
   /* Restore the previous execution state.  */
   set_executing (inferior_ptid, executing);
 
-  return frame;
+  return id;
 }
 
 /* Start replaying a thread.  */
@@ -2031,13 +2031,11 @@ record_btrace_start_replaying (struct thread_info *tp)
      subroutines after we started replaying.  */
   TRY
     {
-      struct frame_info *frame;
       struct frame_id frame_id;
       int upd_step_frame_id, upd_step_stack_frame_id;
 
       /* The current frame without replaying - computed via normal unwind.  */
-      frame = get_thread_current_frame (tp);
-      frame_id = get_frame_id (frame);
+      frame_id = get_thread_current_frame_id (tp);
 
       /* Check if we need to update any stepping-related frame id's.  */
       upd_step_frame_id = frame_id_eq (frame_id,
@@ -2068,8 +2066,7 @@ record_btrace_start_replaying (struct thread_info *tp)
       registers_changed_thread (tp);
 
       /* The current frame with replaying - computed via btrace unwind.  */
-      frame = get_thread_current_frame (tp);
-      frame_id = get_frame_id (frame);
+      frame_id = get_thread_current_frame_id (tp);
 
       /* Replace stepping related frames where necessary.  */
       if (upd_step_frame_id)