This is a note to let you know that I've just added the patch titled

x86/pti/efi: broken conversion from efi to kernel page table

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-pti-efi-broken-conversion-from-efi-to-kernel-page-table.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From pasha.tatashin@oracle.com Sat Jan 13 14:16:28 2018

From: Pavel Tatashin pasha.tatashin@oracle.com Date: Thu, 11 Jan 2018 16:58:20 -0500 Subject: x86/pti/efi: broken conversion from efi to kernel page table To: steven.sistare@oracle.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, gregkh@linuxfoundation.org, jkosina@suse.cz, hughd@google.com, dave.hansen@linux.intel.com, luto@kernel.org, torvalds@linux-foundation.org Message-ID: 20180111215820.29736-1-pasha.tatashin@oracle.com

From: Pavel Tatashin pasha.tatashin@oracle.com

The page table order must be increased for EFI table in order to avoid a bug where NMI tries to change the page table to kernel page table, while efi page table is active.

For more disccussion about this bug, see this thread: http://lkml.iu.edu/hypermail/linux/kernel/1801.1/00951.html

Signed-off-by: Pavel Tatashin pasha.tatashin@oracle.com Reviewed-by: Steven Sistare steven.sistare@oracle.com Acked-by: Jiri Kosina jkosina@suse.cz --- arch/x86/include/asm/pgalloc.h | 11 +++++++++++ arch/x86/platform/efi/efi_64.c | 2 +- 2 files changed, 12 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/pgalloc.h +++ b/arch/x86/include/asm/pgalloc.h @@ -27,6 +27,17 @@ static inline void paravirt_release_pud( */ extern gfp_t __userpte_alloc_gfp;

+#ifdef CONFIG_PAGE_TABLE_ISOLATION +/* + * Instead of one PGD, we acquire two PGDs. Being order-1, it is + * both 8k in size and 8k-aligned. That lets us just flip bit 12 + * in a pointer to swap between the two 4k halves. + */ +#define PGD_ALLOCATION_ORDER 1 +#else +#define PGD_ALLOCATION_ORDER 0 +#endif + /* * Allocate and free page tables. */ --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -142,7 +142,7 @@ int __init efi_alloc_page_tables(void) return 0;

gfp_mask = GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO; - efi_pgd = (pgd_t *)__get_free_page(gfp_mask); + efi_pgd = (pgd_t *)__get_free_pages(gfp_mask, PGD_ALLOCATION_ORDER); if (!efi_pgd) return -ENOMEM;

Patches currently in stable-queue which might be from pasha.tatashin@oracle.com are

queue-4.9/x86-pti-efi-broken-conversion-from-efi-to-kernel-page-table.patch