Re: Report 2 UBSan bugs found by an automatic tool

[Tavian Barnes]

On Sat, 3 Jul 2021 at 11:50, Bernhard Voelker <mail@bernhard-voelker.de> wrote:
>
> Hi James,
>
> On 6/30/21 7:23 PM, He Jingxuan wrote:
> > ...
> > bug 1 command: find -H - -delete
> > relevant error message: ../../find/tree.c:538:23: runtime error: member 
> > access within null pointer of type 'struct predicate’
>
> This is in consider_arm_swap().
> ...
>
> Although I think the first one is a false positive, because the code always 
> ensures
> that the left arm is filled, - and considering the other open bugs related to 
> CBO -,
> maybe it's time to remove that code?

It's not a false positive:

$ git diff
diff --git a/find/tree.c b/find/tree.c
index 1b33edc7..771b92b2 100644
--- a/find/tree.c
+++ b/find/tree.c
@@ -535,6 +535,7 @@ consider_arm_swap (struct predicate *p)
       reason = "Left arm has no child on RHS";
    }
  pr = &p->pred_right;
+  assert(p->pred_left);
  pl = &p->pred_left->pred_right;

  if (!reason)
$ make
...
$ ./find/find nothing -delete
find: tree.c:538: consider_arm_swap: Assertion `p->pred_left' failed.
[2]    94356 abort (core dumped)  ./find/find nothing -delete

-- 
Tavian Barnes