On Fri, Jan 05, 2018 at 10:59:28AM +0100, Thomas Gleixner wrote: > I've seen the insanities which were crammed into the distro kernels, which > have sysctls and whatever, but at the same time these kernels shipped in a
Debugfs tunables only, there are no sysctl, quoting Greg: http://lkml.kernel.org/r/20180107082026.ga11...@kroah.com "It's a debugfs api, it can be changed at any time, to be anything we want, and all is fine :)" > haste do not even boot on a specific class of machines. [..] If you refer to the two efi_64.c and tboot.c corner case boot failures found over the last weekend those affected upstream 4.15-rc 4.14.12 and all PTI branches in linux-tip too (perhaps less reproducible there because of differences in old_memmap handling). I sent you a better version of the efi_64.c fix from Jiri privately and you still miss the tboot fix in linux-tip so you still got a boot failure to fix there. This is incremental with https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/log/?h=WIP.x86/pti where the "Unbreak EFI old_memmap" fix is applied. I respinned it after doing the more correct fix in this case too (same as the efi_64.c improvement) while leaving the attribution to the fix to Dave as he did the hard part. >From 0c480d1eeabd56379144a4ed6b6fb24f3b84e40e Mon Sep 17 00:00:00 2001 From: Dave Hansen <dave.han...@linux.intel.com> Date: Sat, 6 Jan 2018 18:41:14 +0100 Subject: [PATCH 1/1] x86/kaiser/efi: unbreak tboot This is another case similar to what EFI does: create a new set of page tables, map some code at a low address, and jump to it. PTI mistakes this low address for userspace and mistakenly marks it non-executable in an effort to make it unusable for userspace. Undo the poison to allow execution. Signed-off-by: Dave Hansen <dave.han...@linux.intel.com> Cc: Ning Sun <ning....@intel.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@redhat.com> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: x...@kernel.org Cc: tboot-de...@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org Signed-off-by: Andrea Arcangeli <aarca...@redhat.com> --- arch/x86/kernel/tboot.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c index a4eb27918ceb..75869a4b6c41 100644 --- a/arch/x86/kernel/tboot.c +++ b/arch/x86/kernel/tboot.c @@ -127,6 +127,7 @@ static int map_tboot_page(unsigned long vaddr, unsigned long pfn, p4d = p4d_alloc(&tboot_mm, pgd, vaddr); if (!p4d) return -1; + pgd->pgd &= ~_PAGE_NX; pud = pud_alloc(&tboot_mm, p4d, vaddr); if (!pud) return -1; If I can help and assist in any other way let me know. Thanks, Andrea
