Patch "x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface" has been added to the 4.14-stable tree

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

x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-entry-64-clear-registers-for-exceptions-interrupts-to-reduce-speculation-attack-surface.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 <[email protected]> know about it.

From: Dan Williams <[email protected]>
Date: Mon, 5 Feb 2018 17:18:11 -0800
Subject: x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface

From: Dan Williams <[email protected]>

commit 3ac6d8c787b835b997eb23e43e09aa0895ef7d58 upstream.

Clear the 'extra' registers on entering the 64-bit kernel for exceptions and interrupts. The common registers are not cleared since they are likely clobbered well before they can be exploited in a speculative execution attack.

Originally-From: Andi Kleen <[email protected]>

---
 arch/x86/entry/calling.h  |   19 +++++++++++++++++++
 arch/x86/entry/entry_64.S |    6 +++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

@@ -147,6 +147,25 @@ For 32-bit we have the following convent
 	UNWIND_HINT_REGS offset=\offset
 	.endm
 
+	/*
+	 * Sanitize registers of values that a speculation attack
+	 * might otherwise want to exploit. The lower registers are
+	 * likely clobbered well before they could be put to use in
+	 * a speculative execution gadget:
+	 */
+	.macro CLEAR_REGS_NOSPEC
+	xorl %ebp, %ebp
+	xorl %ebx, %ebx
+	xorq %r8, %r8
+	xorq %r9, %r9
+	xorq %r10, %r10
+	xorq %r11, %r11
+	xorq %r12, %r12
+	xorq %r13, %r13
+	xorq %r14, %r14
+	xorq %r15, %r15
+	.endm
+
 	.macro POP_EXTRA_REGS
 	popq %r15
 	popq %r14

@@ -571,6 +571,7 @@ END(irq_entries_start)
 	ALLOC_PT_GPREGS_ON_STACK
 	SAVE_C_REGS
 	SAVE_EXTRA_REGS
+	CLEAR_REGS_NOSPEC
 	ENCODE_FRAME_POINTER
 
 	testb	$3, CS(%rsp)

@@ -1127,6 +1128,7 @@ ENTRY(xen_failsafe_callback)
 	ALLOC_PT_GPREGS_ON_STACK
 	SAVE_C_REGS
 	SAVE_EXTRA_REGS
+	CLEAR_REGS_NOSPEC
 	ENCODE_FRAME_POINTER
 	jmp	error_exit
 END(xen_failsafe_callback)

@@ -1172,6 +1174,7 @@ ENTRY(paranoid_entry)
 	cld
 	SAVE_C_REGS 8
 	SAVE_EXTRA_REGS 8
+	CLEAR_REGS_NOSPEC
 	ENCODE_FRAME_POINTER 8
 	movl	$1, %ebx
 	movl	$MSR_GS_BASE, %ecx

@@ -1224,8 +1227,8 @@ ENTRY(error_entry)
 	cld
 	SAVE_C_REGS 8
 	SAVE_EXTRA_REGS 8
+	CLEAR_REGS_NOSPEC
 	ENCODE_FRAME_POINTER 8
-	xorl	%ebx, %ebx
 	testb	$3, CS+8(%rsp)
 	jz	.Lerror_kernelspace
 

@@ -1422,6 +1425,7 @@ ENTRY(nmi)
 	pushq	%r14		/* pt_regs->r14 */
 	pushq	%r15		/* pt_regs->r15 */
 	UNWIND_HINT_REGS
+	CLEAR_REGS_NOSPEC
 	ENCODE_FRAME_POINTER
 
 	/*

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/x86-entry-64-interleave-xor-register-clearing-with-push-instructions.patch queue-4.14/nospec-move-array_index_nospec-parameter-checking-into-separate-macro.patch queue-4.14/x86-entry-64-merge-the-pop_c_regs-and-pop_extra_regs-macros-into-a-single-pop_regs-macro.patch queue-4.14/kvm-nvmx-set-the-cpu_based_use_msr_bitmaps-if-we-have-a-valid-l02-msr-bitmap.patch queue-4.14/x86-nvmx-properly-set-spec_ctrl-and-pred_cmd-before-merging-msrs.patch queue-4.14/x86-speculation-add-asm-msr-index.h-dependency.patch queue-4.14/x86-entry-64-use-push_and_clean_regs-in-more-cases.patch queue-4.14/x86-speculation-update-speculation-control-microcode-blacklist.patch queue-4.14/x86-entry-64-clear-registers-for-exceptions-interrupts-to-reduce-speculation-attack-surface.patch queue-4.14/x86-speculation-correct-speculation-control-microcode-blacklist-again.patch queue-4.14/x86-entry-64-merge-save_c_regs-and-save_extra_regs-remove-unused-extensions.patch queue-4.14/x86-entry-64-indent-push_and_clear_regs-and-pop_regs-properly.patch queue-4.14/x86-speculation-fix-up-array_index_nospec_mask-asm-constraint.patch queue-4.14/x86-entry-64-clear-extra-registers-beyond-syscall-arguments-to-reduce-speculation-attack-surface.patch queue-4.14/kvm-x86-reduce-retpoline-performance-impact-in-slot_handle_level_range-by-always-inlining-iterator-helper-methods.patch queue-4.14/x86-mm-pti-fix-pti-comment-in-entry_syscall_64.patch queue-4.14/x86-entry-64-get-rid-of-the-alloc_pt_gpregs_on_stack-and-save_and_clear_regs-macros.patch queue-4.14/x86-speculation-clean-up-various-spectre-related-details.patch queue-4.14/x86-entry-64-introduce-the-push_and_clean_regs-macro.patch queue-4.14/revert-x86-speculation-simplify-indirect_branch_prediction_barrier.patch queue-4.14/x86-entry-64-compat-clear-registers-for-compat-syscalls-to-reduce-speculation-attack-surface.patch queue-4.14/x86-entry-64-fix-cr3-restore-in-paranoid_exit.patch