On Fri, Apr 24, 2015 at 4:18 AM, Andy Lutomirski <l...@amacapital.net> wrote: > On Thu, Apr 23, 2015 at 7:15 PM, Andy Lutomirski <l...@kernel.org> wrote: > Even if the issue affects SYSRETQ, it could be that we don't care. If > the extent of the info leak is whether we context switched during a > 64-bit syscall to a non-syscall context, then this is basically > uninteresting. In that case, we could either ignore the 64-bit issue > entirely or fix it the other way: force SS to NULL on context switch > (much faster, I presume) and fix it up before SYSRETL as Denys > suggested. > > We clearly don't have a spate of crashes in programs that do SYSCALL > from a 64-bit CS and then far jump/return to a 32-bit CS without first > reloading SS, since this bug has been here forever. I agree that the > issue is ugly (if it exists in the first place), but maybe we don't > need to fix it.
If you feel that concerned by the speed impact, you can also disable this fix for !CONFIG_IA32_EMULATION kernels. If kernel builder declared they don't want 32-bit userspace, they won't do any ridiculous "I will temporarily switch to 32-bit mode in 64-bit tasks" stuff either. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/