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

x86/kaslr: Fix the vaddr_end mess

to the 4.14-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-kaslr-fix-the-vaddr_end-mess.patch and it can be found in the queue-4.14 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 1dddd25125112ba49706518ac9077a1026a18f37 Mon Sep 17 00:00:00 2001

From: Thomas Gleixner tglx@linutronix.de Date: Thu, 4 Jan 2018 12:32:03 +0100 Subject: x86/kaslr: Fix the vaddr_end mess

From: Thomas Gleixner tglx@linutronix.de

commit 1dddd25125112ba49706518ac9077a1026a18f37 upstream.

vaddr_end for KASLR is only documented in the KASLR code itself and is adjusted depending on config options. So it's not surprising that a change of the memory layout causes KASLR to have the wrong vaddr_end. This can map arbitrary stuff into other areas causing hard to understand problems.

Remove the whole ifdef magic and define the start of the cpu_entry_area to be the end of the KASLR vaddr range.

Add documentation to that effect.

Fixes: 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap") Reported-by: Benjamin Gilbert benjamin.gilbert@coreos.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Benjamin Gilbert benjamin.gilbert@coreos.com Cc: Andy Lutomirski luto@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Garnier thgarnie@google.com, Cc: Alexander Kuleshov kuleshovmail@gmail.com Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801041320360.1771@nanos Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- Documentation/x86/x86_64/mm.txt | 6 ++++++ arch/x86/include/asm/pgtable_64_types.h | 8 +++++++- arch/x86/mm/kaslr.c | 32 +++++++++----------------------- 3 files changed, 22 insertions(+), 24 deletions(-)

--- a/Documentation/x86/x86_64/mm.txt +++ b/Documentation/x86/x86_64/mm.txt @@ -12,6 +12,7 @@ ffffea0000000000 - ffffeaffffffffff (=40 ... unused hole ... ffffec0000000000 - fffffbffffffffff (=44 bits) kasan shadow memory (16TB) ... unused hole ... + vaddr_end for KASLR fffffe0000000000 - fffffe7fffffffff (=39 bits) cpu_entry_area mapping fffffe8000000000 - fffffeffffffffff (=39 bits) LDT remap for PTI ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks @@ -37,6 +38,7 @@ ffd4000000000000 - ffd5ffffffffffff (=49 ... unused hole ... ffdf000000000000 - fffffc0000000000 (=53 bits) kasan shadow memory (8PB) ... unused hole ... + vaddr_end for KASLR fffffe0000000000 - fffffe7fffffffff (=39 bits) cpu_entry_area mapping ... unused hole ... ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks @@ -71,3 +73,7 @@ during EFI runtime calls. Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all physical memory, vmalloc/ioremap space and virtual memory map are randomized. Their order is preserved but their base will be offset early at boot time. + +Be very careful vs. KASLR when changing anything here. The KASLR address +range must not overlap with anything except the KASAN shadow area, which is +correct as KASAN disables KASLR. --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -75,7 +75,13 @@ typedef struct { pteval_t pte; } pte_t; #define PGDIR_SIZE (_AC(1, UL) << PGDIR_SHIFT) #define PGDIR_MASK (~(PGDIR_SIZE - 1))

-/* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */ +/* + * See Documentation/x86/x86_64/mm.txt for a description of the memory map. + * + * Be very careful vs. KASLR when changing anything here. The KASLR address + * range must not overlap with anything except the KASAN shadow area, which + * is correct as KASAN disables KASLR. + */ #define MAXMEM _AC(__AC(1, UL) << MAX_PHYSMEM_BITS, UL)

#ifdef CONFIG_X86_5LEVEL --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -34,25 +34,14 @@ #define TB_SHIFT 40

/* - * Virtual address start and end range for randomization. The end changes base - * on configuration to have the highest amount of space for randomization. - * It increases the possible random position for each randomized region. + * Virtual address start and end range for randomization. * - * You need to add an if/def entry if you introduce a new memory region - * compatible with KASLR. Your entry must be in logical order with memory - * layout. For example, ESPFIX is before EFI because its virtual address is - * before. You also need to add a BUILD_BUG_ON() in kernel_randomize_memory() to - * ensure that this order is correct and won't be changed. + * The end address could depend on more configuration options to make the + * highest amount of space for randomization available, but that's too hard + * to keep straight and caused issues already. */ static const unsigned long vaddr_start = __PAGE_OFFSET_BASE; - -#if defined(CONFIG_X86_ESPFIX64) -static const unsigned long vaddr_end = ESPFIX_BASE_ADDR; -#elif defined(CONFIG_EFI) -static const unsigned long vaddr_end = EFI_VA_END; -#else -static const unsigned long vaddr_end = __START_KERNEL_map; -#endif +static const unsigned long vaddr_end = CPU_ENTRY_AREA_BASE;

/* Default values */ unsigned long page_offset_base = __PAGE_OFFSET_BASE; @@ -101,15 +90,12 @@ void __init kernel_randomize_memory(void unsigned long remain_entropy;

/* - * All these BUILD_BUG_ON checks ensures the memory layout is - * consistent with the vaddr_start/vaddr_end variables. + * These BUILD_BUG_ON checks ensure the memory layout is consistent + * with the vaddr_start/vaddr_end variables. These checks are very + * limited.... */ BUILD_BUG_ON(vaddr_start >= vaddr_end); - BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) && - vaddr_end >= EFI_VA_END); - BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) || - IS_ENABLED(CONFIG_EFI)) && - vaddr_end >= __START_KERNEL_map); + BUILD_BUG_ON(vaddr_end != CPU_ENTRY_AREA_BASE); BUILD_BUG_ON(vaddr_end > __START_KERNEL_map);

if (!kaslr_memory_enabled())

Patches currently in stable-queue which might be from tglx@linutronix.de are

queue-4.14/x86-tlb-drop-the-_gpl-from-the-cpu_tlbstate-export.patch queue-4.14/x86-alternatives-add-missing-n-at-end-of-alternative-inline-asm.patch queue-4.14/x86-kaslr-fix-the-vaddr_end-mess.patch queue-4.14/efi-capsule-loader-reinstate-virtual-capsule-mapping.patch queue-4.14/x86-mm-set-modules_end-to-0xffffffffff000000.patch queue-4.14/mm-sparse.c-wrong-allocation-for-mem_section.patch queue-4.14/x86-events-intel-ds-use-the-proper-cache-flush-method-for-mapping-ds-buffers.patch queue-4.14/x86-pti-rename-bug_cpu_insecure-to-bug_cpu_meltdown.patch queue-4.14/x86-mm-map-cpu_entry_area-at-the-same-place-on-4-5-level.patch