On Wed, Dec 3, 2014 at 3:37 PM, Andrew Morton <a...@linux-foundation.org> wrote: > On Mon, 1 Dec 2014 06:55:01 -0800 Andy Lutomirski <l...@amacapital.net> wrote: > >> On Tue, Nov 11, 2014 at 2:52 AM, Richard Weinberger <rich...@nod.at> wrote: >> > Am 11.11.2014 um 03:13 schrieb David Miller: >> >> From: Andy Lutomirski <l...@amacapital.net> >> >> Date: Mon, 10 Nov 2014 14:03:23 -0800 >> >> >> >>> On Wed, Oct 29, 2014 at 11:12 AM, Thomas Gleixner <t...@linutronix.de> >> >>> wrote: >> >>>> On Wed, 29 Oct 2014, Andy Lutomirski wrote: >> >>>> >> >>>>> If an attacker can cause a controlled kernel stack overflow, >> >>>>> overwriting the restart block is a very juicy exploit target. >> >>>>> Moving the restart block to struct task_struct prevents this >> >>>>> exploit. >> >>>>> >> >>>>> Note that there are other fields in thread_info that are also easy >> >>>>> targets, at least on some architectures. >> >>>>> >> >>>>> It's also a decent simplification, since the restart code is more or >> >>>>> less identical on all architectures. >> >>>> >> >>>> I think that's the most important change. Moving common stuff into >> >>>> common code. The side effect of slightly reducing the attack surface >> >>>> is nice, but as Al pointed out not really the big win here. >> >>> >> >>> Having gotten exactly zero feedback from any arch maintainer outside >> >>> of x86, am I supposed to pester people further? >> >> >> >> No objections wrt. sparc and if things break I'll help fix it. >> > >> > Same for UML. >> > Acked-by: Richard Weinberger <rich...@nod.at> >> >> akpm, do you consider this appropriate for either 3.19 or 3.20? If >> so, can you add it to the appropriate part of -mm? > > Yes, I can grab it. Probably for .20, as the lag times for exposing > issues in obscures architectures are lengthy. > > One clarification: > > : If an attacker can cause a controlled kernel stack overflow, > : overwriting the restart block is a very juicy exploit target. > > This is because the thread_info actually resides in the memory which > was allocated for the kernel stack, yes? Whereas the task_struct is > separately allocated and is harder to find?
Yes, exactly. > > Spelling this out in the changelog would be useful for the ignorant and > the forgetful ;) Want a new version, or will you fix it up yourself? Thanks, Andy > > : Moving the restart block to struct task_struct prevents this > : exploit. > > -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
