Date: Wed, 9 Mar 2016 15:07:07 -0700 From: Scotty Bauer <sbauer@....utah.edu> To: Ingo Molnar <mingo@...nel.org> Cc: linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com, x86@...nel.org, wmealing@...hat.com, ak@...ux.intel.com, luto@...capital.net, Abhiram Balasubramanian <abhiram@...utah.edu>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH v3 1/3] SROP Mitigation: Architecture independent code for signal cookies On 03/09/2016 01:32 AM, Ingo Molnar wrote: > > * Scott Bauer <sbauer@....utah.edu> wrote: > >> This patch adds a per-process secret to the task struct which >> will be used during signal delivery and during a sigreturn. >> Also, logic is added in signal.c to generate, place, extract, >> clear and verify the signal cookie. > >> /* >> + * Canary value for signal frames placed on user stack. >> + * This helps mitigate "Signal Return oriented program" >> + * exploits in userland. >> + */ >> + unsigned long sig_cookie; > > Could you please add a high level description in Documentation > that explains the attack and the way how this mitigation code > prevents that kind of attack? > > Also, the first changelogs should contain more high level > description as well. For example, what does the 'verification' > of the signal cookie mean, and how does it prevent an SROP > attempt? > > All of these patches seem to assume that people reading this code > know what SROP is and how we defend against it - that is not so. > > Thanks, > > Ingo > I'm going to submit v4 to fix some nits where I'll include the explanation and a change log, I apologize for not doing that here. In the meantime if you don't mind visiting a link I included a brief explanation on previous versions of the patch set. https://lkml.org/lkml/2016/2/6/166 Thanks
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