[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 0/12] xen: arm: reenable support for 32-bit userspace running in 64-bit guest.
XSA-102/CVE-2014-5147[0] concerned a crash when trapping from 32-bit userspace in a 64-bit guest. Part of that security patch was c0020e09970 "xen: arm: Handle traps from 32-bit userspace on 64-bit kernel as undef fix" which turned the exploitable crash into a #undef to the guest (so as to kill the process but not the host) as a workaround for the issue. However while this prevented the exploit it did not make 32-bit userspaces which were prone to triggering the issue actually work. This series consists of some patches which I originally wrote for XSA-102 to fix the issue properly before it was determined that those fixes were too invasive by far for a security update. At the end of the series is a new patch which removes the XSA-102 workaround since all problematic traps should now be handled. Since these were originally intended to be the security fix they have had a fair bit of scrutiny already in private . However since there is now a risk of reintroducing XSA-102 I would appreciate a pretty thorough second pair of eyes on it this time around. I've tested this with a local utility which tries to access the various cp and system registers from both 32- and 64-bit processes and checks that they either work or give the expected traps. Since this tool is effectively an exploit for XSA-102 I'm not sharing here but if you ask nicely and appear to be wearing the correct colour hat I might share it with you (it's not terribly impressive, so don't get too excited). Since last time I've implemented Julien's review feedback including: * added the GUEST_BUG_ON patch to the end to replace the BUG_ONs due to invalid h/w state, which gets more useful debug if that occurs. * handled CNTP_CVAL_EL0. Ian. [0] http://xenbits.xen.org/xsa/advisory-102.html _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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