Re: [PATCH] Fix read after xfree in linux_nat_detach

[Pedro Alves <palves@redhat.com>]

On 03/22/2017 01:11 PM, Philipp Rudo wrote:
> At the end of linux_nat_detach there is a check whether the inferior has a
> fork.  If no fork exists the main_lwp is detached (detach_one_lwp) and
> later, outside the check, deleted (delete_lwp).  This is problematic as
> detach_one_lwp also calls delete_lwp freeing main_lwp.  Thus the second
> call to delete_lwp reads from already freed memory.  Fix this by removing
> delete_lwp at the end of detach_one_lwp.

Why not just move that unconditional call to delete_lwp call at
the end of linux_nat_detach to the forks_exist_p/true branch?

Actually, that call looks unnecessary for the fork case too,
since we have:

  linux_fork_detach
    -> fork_load_infrun_state
      -> linux_nat_switch_fork
         -> purge_lwp_list
            -> lwp_lwpid_htab_remove_pid
               -> lwp_free

So... couldn't we just remove that delete_lwp line and be done with it?

Thanks,
Pedro Alves