Re: [PATCH 1/2] proc: protect ptrace_may_access() with exec_update_lock (part 1)

[Oleg Nesterov <oleg@redhat.com>]

Perhaps proc_pid_make_inode() can record task->self_exec_id in
proc_inode ? At least this can help to fix the
"if (ptrace_may_access(task)) mm = get_task_mm(task)" pattern...

On 05/26, Oleg Nesterov wrote:
>
> On 05/18, Jann Horn wrote:
> >
> > Fix the easy cases where procfs currently calls ptrace_may_access() without
> > exec_update_lock protection, where the fix is to simply add the extra lock
> > or use mm_access():
>
> I thought about this too, but I do not know if it is fine performance wise...
>
> And what about proc_coredump_filter_write() which doesn't use ptrace_may_access() ?
>
> AFAICS, we can't rely on the open-time checks. /proc/$pid/coredump_filter can
> be opened for writing, the task can do suid exec after that, the file remains
> writable.
>
> Not a big deal, but still.
>
> Oleg.