From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758541AbbIDMev (ORCPT ); Fri, 4 Sep 2015 08:34:51 -0400 Received: from mail-io0-f182.google.com ([209.85.223.182]:34576 "EHLO mail-io0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752296AbbIDMeu (ORCPT ); Fri, 4 Sep 2015 08:34:50 -0400 Subject: Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') To: Stas Sergeev , Chuck Ebbert References: <55E6C36F.6080309@list.ru> <55E736E9.2000201@list.ru> <55E7607B.4070800@list.ru> <55E7663B.30402@list.ru> <55E76FCB.7090304@list.ru> <55E838E6.8060205@gmail.com> <55E839C7.8010501@list.ru> <55E86AF7.3090200@gmail.com> <55E8767A.7000408@list.ru> <55E896C7.1010500@gmail.com> <55E8BB64.3020906@list.ru> <20150904060933.229b5b06@as> <55E9767B.2020501@list.ru> Cc: Andy Lutomirski , Josh Boyer , linux-kernel@vger.kernel.org, "Andrew Bird (Sphere Systems)" , Linus Torvalds , Ingo Molnar , Kees Cook , Brian Gerst From: Austin S Hemmelgarn Message-ID: <55E98FD7.8020809@gmail.com> Date: Fri, 4 Sep 2015 08:34:31 -0400 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <55E9767B.2020501@list.ru> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms040404070401020303070009" X-Antivirus: avast! (VPS 150904-0, 2015-09-04), Outbound message X-Antivirus-Status: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a cryptographically signed message in MIME format. --------------ms040404070401020303070009 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-04 06:46, Stas Sergeev wrote: > 04.09.2015 13:09, Chuck Ebbert =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On Fri, 4 Sep 2015 00:28:04 +0300 >> Stas Sergeev wrote: >> >>> 03.09.2015 21:51, Austin S Hemmelgarn =D0=BF=D0=B8=D1=88=D0=B5=D1=82:= >>>> There are servers out there that have this enabled and _never_ use i= t >>>> at all, >>> Unless I am mistaken, servers usually use special flavour of the >>> distro (different from desktop install), where of course this will >>> be disabled _compile time_. >> Many (most?) distros use just one kernel for everything, because it's >> just too much work to have a separate flavor for servers. > But for example menuconfig promotes CONFIG_PREEMPT_NONE for server > and CONFIG_PREEMPT for desktop. Also perhaps server would need an > lts version rather than latest. > I wonder if RHEL Server offers the generic desktop-suited kernel > with vm86() enabled? > > In any case, if there is some generic mechanism to selectively > disable syscalls at run-time for server, then vm86() is of course > a good candidate. I wonder how many other syscalls are currently > run-time controlled? (those that are not marked as an "attack surface" > and defaulted to Y; I suppose the "attack surface" is currently only vm= 86()) > OK, I think I need to clarify something here. The attack surface of a given system refers to the number of different=20 ways that someone could potentially attack that system. An individual=20 syscall is not in itself an attack surface, but is part of the attack=20 surface for the whole system. One of the core concepts of proactive=20 security is to minimize the attack surface, because the fewer ways=20 someone could possibly attack you, the less likely it is that they will=20 succeed. I however, referred to vm86 as a potential attack vector, which refers=20 one way in which someone could attempt to attack the system (be it=20 through arbitrary code execution , privilege escalation, or some other=20 type of exploit), note that something does not need to have a known=20 exploit to be classified as a potential attack vector (most black hat's=20 out there will keep quiet about discovered exploits until they can=20 actually make use of them themselves). By their very definition, every=20 single site that userspace can call into the kernel is a _potential_=20 attack vector, including vm86(). vm86() is one of the more attractive=20 syscalls to attempt to use as an attack vector on 32-bit x86 systems=20 because it's relatively unaudited, significantly modifies the execution=20 state of the processor, and is available on a majority of 32-bit x85=20 systems in the wild. This does not mean that it is exploitable=20 directly, just that it's a possible target for an exploit. --------------ms040404070401020303070009 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC Brgwgga0MIIEnKADAgECAgMQblUwDQYJKoZIhvcNAQENBQAweTEQMA4GA1UEChMHUm9vdCBD QTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNp Z25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcwHhcN MTUwMzI1MTkzNDM4WhcNMTUwOTIxMTkzNDM4WjBjMRgwFgYDVQQDEw9DQWNlcnQgV29UIFVz ZXIxIzAhBgkqhkiG9w0BCQEWFGFoZmVycm9pbjdAZ21haWwuY29tMSIwIAYJKoZIhvcNAQkB FhNhaGVtbWVsZ0BvaGlvZ3QuY29tMIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEA nQ/81tq0QBQi5w316VsVNfjg6kVVIMx760TuwA1MUaNQgQ3NyUl+UyFtjhpkNwwChjgAqfGd LIMTHAdObcwGfzO5uI2o1a8MHVQna8FRsU3QGouysIOGQlX8jFYXMKPEdnlt0GoQcd+BtESr pivbGWUEkPs1CwM6WOrs+09bAJP3qzKIr0VxervFrzrC5Dg9Rf18r9WXHElBuWHg4GYHNJ2V Ab8iKc10h44FnqxZK8RDN8ts/xX93i9bIBmHnFfyNRfiOUtNVeynJbf6kVtdHP+CRBkXCNRZ qyQT7gbTGD24P92PS2UTmDfplSBcWcTn65o3xWfesbf02jF6PL3BCrVnDRI4RgYxG3zFBJuG qvMoEODLhHKSXPAyQhwZINigZNdw5G1NqjXqUw+lIqdQvoPijK9J3eijiakh9u2bjWOMaleI SMRR6XsdM2O5qun1dqOrCgRkM0XSNtBQ2JjY7CycIx+qifJWsRaYWZz0aQU4ZrtAI7gVhO9h pyNaAGjvm7PdjEBiXq57e4QcgpwzvNlv8pG1c/hnt0msfDWNJtl3b6elhQ2Pz4w/QnWifZ8E BrFEmjeeJa2dqjE3giPVWrsH+lOvQQONsYJOuVb8b0zao4vrWeGmW2q2e3pdv0Axzm/60cJQ haZUv8+JdX9ZzqxOm5w5eUQSclt84u+D+hsCAwEAAaOCAVkwggFVMAwGA1UdEwEB/wQCMAAw VgYJYIZIAYb4QgENBEkWR1RvIGdldCB5b3VyIG93biBjZXJ0aWZpY2F0ZSBmb3IgRlJFRSBo ZWFkIG92ZXIgdG8gaHR0cDovL3d3dy5DQWNlcnQub3JnMA4GA1UdDwEB/wQEAwIDqDBABgNV HSUEOTA3BggrBgEFBQcDBAYIKwYBBQUHAwIGCisGAQQBgjcKAwQGCisGAQQBgjcKAwMGCWCG SAGG+EIEATAyBggrBgEFBQcBAQQmMCQwIgYIKwYBBQUHMAGGFmh0dHA6Ly9vY3NwLmNhY2Vy dC5vcmcwMQYDVR0fBCowKDAmoCSgIoYgaHR0cDovL2NybC5jYWNlcnQub3JnL3Jldm9rZS5j cmwwNAYDVR0RBC0wK4EUYWhmZXJyb2luN0BnbWFpbC5jb22BE2FoZW1tZWxnQG9oaW9ndC5j b20wDQYJKoZIhvcNAQENBQADggIBABr5e8W+NiTER+Q/7wiA2LxWN3UdhT3eZJjqqSlP370P KL5iWqeTfxQ67Ai/mHbJcT2PgAJ+/D2Ji+aRR03UWnU/vtOwzyDLUMstqnfl0Zs+sz/CJe7x nBA5jlpjC2DKuMVfbPze7eySaen7XSGFHKE1QoVIIpQ2kVjC4nbbJQnUbAVX1Iz29WxeVGt9 XYigz3tDPf3tglN+q23E7YjQl4abTIoM7i98yV1H9gfY8lFfKZ6jREB9+n6ie2EwS3Kat2mG tl2wBx4MfRnoSQSKsLKQ5oTwhWf0JqlFwpLfl374p0Njcykej9/jnWG8Ks1V/AXTHqI4eyIP Mf5yMZkPv7n7LS9WWKdG4Nd38iv4T2EiAaWsmgu+r81qL5CJu9AyA0SBS4ttKf6k3e63w2Mv N9R45vpQ3QhAhfWyFxFhZN95APe3YECDG3+XIRJpRYPEtHuIsOyzI70ajF93gg/BidvqKsmV MM2ccktDMfqwZXea6zey7F8Geu9R7BqjXmG2HlNuXu7e/xnHOgXf5D3wPmnRLlBhXL1Ch97a w2KjaupjpAHfFjv5kGnZXN87UvvlwzIZiKXwa3vTDwK+rrKn/sHPkfDZPSiyt/ZBIK6lX83P 34H/CzGg+Kx57rHYOIHGumIvpDa5vfWp8O0sGgawb1C2Aae4sTUVIWmIjVuGI062MYIE0TCC BM0CAQEwgYAweTEQMA4GA1UEChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNl cnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcN AQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxBuVTANBglghkgBZQMEAgMFAKCCAiEwGAYJKoZI hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTA0MTIzNDMxWjBPBgkq hkiG9w0BCQQxQgRA1329YwVoWRA7Zv1t4YZCODAmUNT7+C4OuAiRiWTf/o10gYwOXL6oi3Op o5Lk7LIqxlh2GquiVo0KzDSRWiYgJTBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxBuVTCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxBuVTAN BgkqhkiG9w0BAQEFAASCAgCIzeb9KRZRZfp0gV3a0IPkw12UCyfiWZ7QInyzn/VR1Xr9CRBF oWhsqGdvY4unCEM73h+tkMn3umJSmzF6YiRqv9fk4mpc/UPW6Gb9gsDYP0RZX2eRRuY94ayu OuR4u4NXs3VD21+qSg28/aZUJmbzjSQggn+Ob52SNuP/chZL3SGNjyfcwDErC7gQ/JZiCESV sA16OMX/OIIINuQEBkGp1GRvQWhJOWXLCfA1EdtY3t6uHQpbsTTvegtXsKC/ROS0YdZo6k0W 1eaECe2LATR51GkuaB0H0V+KS8UTryoaeYp0Nb9L2GoeVhygKhVnLeZ0/iZXBQxicRsxmBC9 jqAADS6F05L7kXNt8uRT6w7saWFomoJkfDyo0kigtziVMi7Tnzr7t3AOcfMRaCbpCQHUQr6O Tmx3vKwn5x3ZAyDD1VQeBIsSFSu64/rKmn12V2j91EssD8j4aV+KBrNlDXRBrkC0ecWm+9QZ imQVxpFgxc9D1wLR+MPPRLOzqoIs1vxKbf5W+5Rr3hLGGdL9ZwSatdH4IqAGRRd3jbEYkyF4 1XsqtfceogSm11nHCzfGv6eiDRrcGzg63Cp6Dc7omeQQl+j5ulbrdUyUL78h6z8hNIH2iwbp fh814BV3Xnlv6erTRPm4eF/X+wyuRDgVcztQRBcZmS4eNXy3R4k/VVUaegAAAAAAAA== --------------ms040404070401020303070009--