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Date: Sat, 15 Feb 2014 00:06:22 +0400 From: Cyrill Gorcunov <gorcunov@...il.com> To: Pavel Emelyanov <xemul@...allels.com> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, Andrew Vagin <avagin@...il.com>, Aditya Kali <adityakali@...gle.com>, Stephen Rothwell <sfr@...b.auug.org.au>, Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org, criu@...nvz.org, Al Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org> Subject: Re: [CRIU] [PATCH 1/3] prctl: reduce permissions to change boundaries of data, brk and stack On Fri, Feb 14, 2014 at 11:47:13PM +0400, Pavel Emelyanov wrote: > >> Maybe we could improve this api and provide argument as a pointer > >> to a structure, which would have all the fields we're going to > >> modify, which in turn would allow us to verify that all new values > >> are sane and fit rlimits, then we could (probably) deprecate old > >> api if noone except c/r camp is using it (I actually can't imagine > >> who else might need this api). Then CAP_SYS_RESOURCE requirement > >> could be ripped off. Hm? (sure touching api is always "no-no" > >> case, but maybe...) > > > > Hmm. Let me rewind this a little bit. > > > > I want to be very stupid and ask the following. > > > > Why can't you have the process of interest do: > > ptrace(PTRACE_ATTACHME); > > execve(executable, args, ...); > > > > /* Have the ptracer inject the recovery/fixup code */ > > /* Fix up the mostly correct process to look like it has been > > * executing for a while. > > */ Erik, it seems I don't understand how it will help us to restore the mm fields mentioned above? > Let's imagine we do that. > > This means, that the whole memory contents should be restored _after_ > the execve() call, since the execve() flushes old mappings. In > that case we lose the ability to preserve any shared memory regions > between any two processes. This "shared" can be either regular > MAP_SHARED mappings or MAP_ANONYMOUS but still not COW-ed ones. > > > That should work, set all of the interesting fields, and works as > > non-root today. My gut feel says do that and we can just > > deprecate/remove prctl_set_mm. > > > > I am hoping we can move this conversation what makes sense from oh ick > > checkpoint/restort does not work with user namespaces. I fear you've got a wrong impression that we're "ick'ing" about user-ns ;) Actually it's "must have" feature for containers thus we would _really_ love to be able to c/r them. -- 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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