Re: + prctl-pr_set_mm-introduce-pr_set_mm_map-operation-v3.patch added to -mm tree

Oleg Nesterov
2014-08-23T13:32:38Z

forgot to mention,

On 08/23, Oleg Nesterov wrote:
>
> On 08/23, Cyrill Gorcunov wrote:
>
> > Looks like I need
> > to use cred_guard_mutex instead of task_lock here, no?
>
> Please don't. First of all, it can't help because proc_pid_auxv() doesn't hold
> this lock. It does mm_access() which drops this lock after return. And to remind,
> we are going to remove mm_access/lock_trace from sys_read() paths in proc.

Besides, it can't help anyway. cred_guard_mutex is per-process (not per-thread),
suppose that a vfork()'ed child does prctl() while another thread reads the
parent's /proc/pid/auxv.

Cyrill, I am sorry, but I am starting to think that this patch should be
dropped and replaced by another version. Or do you think it would be better
to send the fixes on top?

Oleg.