Re: [PATCH] xacct_add_tsk: fix pure theoretical ->mm use-after-free

[Oleg Nesterov]

On 10/30, Jay Lan wrote:
>
> Oleg Nesterov wrote:
> > Paranoid fix. The task can free its ->mm after the 'if (p->mm)' check.
> 
> Why this change is necessary? This routine is indirectly invoked by
> taskstats_exit_send() routine called inside do_exit():

Not only, please note

	taskstats_user_cmd(TASKSTATS_CMD_ATTR_PID)->fill_pid()->xacct_add_tsk()

path. This tsk is not 'current', it was found by find_task_by_pid(), and
it may exit at any time.

Oleg.

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