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Date: Tue, 8 Dec 2009 14:56:40 +0900 (JST) From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> To: Ingo Molnar <mingo@...e.hu> Cc: kosaki.motohiro@...fujitsu.com, Bryan Donlan <bdonlan@...il.com>, Ulrich Drepper <drepper@...hat.com>, Timo Sirainen <tss@....fi>, WANG Cong <xiyou.wangcong@...il.com>, Oleg Nesterov <oleg@...hat.com>, LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH v6] Added PR_SET_PROCTITLE_AREA option for prctl() > > * KOSAKI Motohiro <kosaki.motohiro@...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. > > [...] I don't want any task allow to change another task's memory > > except ptrace. > > And i did not mean to allow 'any' task to be allowed to do this - > security checks apply, obviously. Agreed. My 'any' didn't intent bypass security check ;-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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