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Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies

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On 03/29/2016 03:29 PM, Andy Lutomirski wrote:
> On Tue, Mar 29, 2016 at 12:53 PM, Scott Bauer <sbauer@eng.utah.edu> wrote:
>> Sigreturn-oriented programming is a new attack vector in userland
>> where an attacker crafts a fake signal frame on the stack and calls
>> sigreturn. The kernel will extract the fake signal frame, which
>> contains attacker controlled "saved" registers. The kernel will then
>> transfer control to the attacker controlled userland instruction pointer.
>>
>> To prevent SROP attacks the kernel needs to know or be able to dervive
>> whether a sigreturn it is processing is in response to a legitimate
>> signal the kernel previously delivered.
>>
>> Further information and test code can be found in Documentation/security
>> and this excellent article:
>> http://lwn.net/Articles/676803/
>>
>> These patches implement the necessary changes to generate a cookie
>> which will be placed above signal frame upon signal delivery to userland.
>> The cookie is generated using a per-process random value xor'd with
>> the address where the cookie will be stored on the stack.
>>
>> Upon a sigreturn the kernel will extract the cookie from userland,
>> recalculate what the original cookie should be and verify that the two
>> do not differ. If the two differ the kernel will terminate the process
>> with a SIGSEGV.
>>
>> This prevents SROP by adding a value that the attacker cannot guess,
>> but the kernel can verify. Therefore an attacker cannot use sigreturn as
>> a method to control the flow of a process.
>>
> 
> Has anyone verified that this doesn't break CRIU cross-machine (or
> cross-boot) migration and that this doesn't break dosemu?  You're
> changing the ABI here.
> 

I haven't yet I'll do that to verify it breaks -- I'm pretty sure under some
conditions it will break CRIU. That's why we added the sysctl to turn it off. 
Should I have mentioned this in the main commit that it possibly breaks CRIU/DOSEMU?
I went ahead and added that to the Documentation.

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[PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Scott Bauer <sbauer@eng.utah.edu> - 2016-03-29 22:00 +0200
  [PATCH v4 1/4] SROP Mitigation: Architecture independent code for signal cookies Scott Bauer <sbauer@eng.utah.edu> - 2016-03-29 22:00 +0200
    Re: [PATCH v4 1/4] SROP Mitigation: Architecture independent code for  signal cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-30 01:10 +0200
    Re: [PATCH v4 1/4] SROP Mitigation: Architecture independent code for signal cookies ebiederm@xmission.com (Eric W. Biederman) - 2016-03-31 22:40 +0200
      Re: [PATCH v4 1/4] SROP Mitigation: Architecture independent code for  signal cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-01 00:10 +0200
        Re: [PATCH v4 1/4] SROP Mitigation: Architecture independent code for signal cookies ebiederm@xmission.com (Eric W. Biederman) - 2016-04-01 00:30 +0200
  Re: [PATCH v4 3/4] Sysctl: SROP Mitigation: Add Sysctl argument to  disable SROP. Andi Kleen <ak@linux.intel.com> - 2016-03-29 22:00 +0200
    Re: [PATCH v4 3/4] Sysctl: SROP Mitigation: Add Sysctl argument to  disable SROP. Scotty Bauer <sbauer@eng.utah.edu> - 2016-03-29 22:50 +0200
      Re: [PATCH v4 3/4] Sysctl: SROP Mitigation: Add Sysctl argument to  disable SROP. Andi Kleen <ak@linux.intel.com> - 2016-03-29 23:00 +0200
  [PATCH v4 3/4] Sysctl: SROP Mitigation: Add Sysctl argument to disable SROP. Scott Bauer <sbauer@eng.utah.edu> - 2016-03-29 22:00 +0200
  [PATCH v4 2/4] x86: SROP Mitigation: Implement Signal Cookies Scott Bauer <sbauer@eng.utah.edu> - 2016-03-29 22:00 +0200
  Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Andy Lutomirski <luto@amacapital.net> - 2016-03-29 23:30 +0200
    Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Andy Lutomirski <luto@amacapital.net> - 2016-03-29 23:40 +0200
      Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-30 00:40 +0200
        Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Scotty Bauer <sbauer@eng.utah.edu> - 2016-03-30 01:20 +0200
          Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies ebiederm@xmission.com (Eric W. Biederman) - 2016-03-31 22:40 +0200
            Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Cyrill Gorcunov <gorcunov@gmail.com> - 2016-04-01 15:00 +0200
      Re: [kernel-hardening] Re: [PATCH v4 0/4] SROP Mitigation:  Sigreturn Cookies Daniel Micay <danielmicay@gmail.com> - 2016-03-30 01:00 +0200
    Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Scotty Bauer <sbauer@eng.utah.edu> - 2016-03-29 23:40 +0200
  Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-30 01:00 +0200
    Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-30 01:00 +0200
    Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Andy Lutomirski <luto@amacapital.net> - 2016-03-30 01:10 +0200
    Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Scotty Bauer <sbauer@eng.utah.edu> - 2016-03-30 01:20 +0200
      Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-30 01:30 +0200
        Re: [PATCH v4 0/4] SROP Mitigation: Sigreturn Cookies Scotty Bauer <sbauer@eng.utah.edu> - 2016-03-30 01:40 +0200

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