[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/xen: Fix 32-bit PV guests's usage of kernel_stack
On 04/09/2014 11:01 AM, Jan Beulich wrote: On 09.04.14 at 16:41, <andrew.cooper3@xxxxxxxxxx> wrote:The latter load however can easy fault; The arguments for %ds in XSA-42/ CVE-2013-0228 applies to %{e,f,g}s as well.And it was only that latter operation that I pointed at. We don't seem to reference %fs after the pop so doing the fixup (as David suggested) should be enough? -boris Furthermore, I am a little concerned about the performance impact of this. I would have thought that in most cases, %fs will already be correct, at which point reloading it twice is a waste of time.Why would you expect %fs on the IRET path to commonly point to the kernel segment rather than whatever user mode wants/needs? Also, I'm not sure adding conditionals here wouldn't harm performance about as much as the save/load/restore. If anything I'd look into open coding GET_THREAD_INFO() without using %fs for this single case. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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