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Date: Wed, 13 Sep 2017 19:11:35 +0200 From: Oleg Nesterov <oleg@...hat.com> To: Jürg Billeter <j@...ron.ch> Cc: Andrew Morton <akpm@...ux-foundation.org>, Eric Biederman <ebiederm@...ssion.com>, linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Michael Kerrisk <mtk.manpages@...il.com> Subject: Re: [PATCH] prctl: add PR_[GS]ET_PDEATHSIG_PROC On 09/12, Jürg Billeter wrote: > > On Tue, 2017-09-12 at 19:05 +0200, Oleg Nesterov wrote: > > On 09/09, Jürg Billeter wrote: > > > Unlike > > > PR_SET_PDEATHSIG, this is inherited across fork to allow killing a whole > > > subtree without race conditions. > > > > but I am still not sure this is right... at least I can't understand the > > "without race conditions" above. > > > > IOW, the child can do prctl(PR_SET_PDEATHSIG_PROC, SIGKILL) right after fork(), > > why this is not enough to kill a whole subtree without race conditions? > > What if the parent dies between fork() and prctl()? The child will be killed? Sorry, can't understand... > it also makes it relatively easy to enforce > PDEATHSIG_PROC for all descendants of a process. this is clear, > > Say, CLONE_PARENT. Should it succeed if ->pdeath_signal_proc != 0 ? > > Yes, I don't see an issue with that. The new process will be a sibling > and inheriting pdeath_signal_proc seems sensible to me for this. I meant, the process created by clone(CLONE_PARENT) won't be killed by pdeath_signal if the creator process exits, exactly because it won't be its child. Not that I think this is wrong. Oleg.
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