verified that this:
> diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
> index 1f62cf3e6652..8eb63eb3dc37 100644
> --- a/sys/kern/vfs_lookup.c
> +++ b/sys/kern/vfs_lookup.c
> @@ -1240,7 +1240,13 @@ vfs_lookup(struct nameidata *ndp)
> #endif
> ndp->ni_dvp = dp;
> ndp->ni_vp = NULL;
> ASSERT_VOP_LOCKED(dp, "lookup");
> +
> + DEBUG_POISON_POINTER(dp);
> + printf("%s: read off dp %p\n", __func__, dp);
> + printf("%s: deref dp->v_mount %p\n", __func__, dp->v_mount);
> +
> /*
> * If we have a shared lock we may need to upgrade the lock for the
> * last operation.
>
without kasan: prints the first line, traps on the other
with kasan: it traps on the first printf