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SubjectRe: [PATCH v6] Added PR_SET_PROCTITLE_AREA option for prctl()
Date
> > 
> > * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> >
> > > > The feature looks useful, but the choice of a prctl as an API is strange
> > > > - it limits us to the current task only - while the ability to set
> > > > arguments for another task looks a more generic (and potentially more
> > > > useful) solution.
> > >
> > > No. It's impossible.
> > > /proc/{pid}/cmdline read user process's memory. iow, this prctl() don't
> > > receive string, it receive virtual address itself. [...]
> >
> > it's not 'impossible' at all, you yourself mention ptrace:
>
> Ah yes, 'impossible' was wrong word. but it doesn't works intentionally.
>
> 1. setproctitle() unaware application continue to see argv[0] directly.
> it makes some inconsistent behavior.
> 2. proc title (i.e. string) injection need to map new page as process title area.
> implicit mapping increasing makes new trouble
> - mihgt cause to exceed max_map_count awhile after.
> - might cause leak proc title area (who know when it should be freed?)
>
> I think reasonable way is 1. send signal (or use another inter process
> communication way) to target process 2. target process change own proc title
> themself.
>
> Plus, I haven't seen the use-case of changin another task. iow I doubt
> it's worth to change lots code.

if your mention is strongly, can you please explain your expected use case?




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