2018-01-15 11:26:15 +00:00
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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2018-01-06 14:13:39 +00:00
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From: Andy Lutomirski <luto@kernel.org>
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Date: Thu, 2 Nov 2017 00:59:01 -0700
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2018-01-15 11:26:15 +00:00
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Subject: [PATCH] x86/entry/64: Simplify reg restore code in the standard IRET
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paths
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2018-01-06 14:13:39 +00:00
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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CVE-2017-5754
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The old code restored all the registers with movq instead of pop.
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In theory, this was done because some CPUs have higher movq
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throughput, but any gain there would be tiny and is almost certainly
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outweighed by the higher text size.
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This saves 96 bytes of text.
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Signed-off-by: Andy Lutomirski <luto@kernel.org>
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Cc: Borislav Petkov <bpetkov@suse.de>
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Cc: Brian Gerst <brgerst@gmail.com>
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Cc: Dave Hansen <dave.hansen@intel.com>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Link: http://lkml.kernel.org/r/ad82520a207ccd851b04ba613f4f752b33ac05f7.1509609304.git.luto@kernel.org
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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(cherry picked from commit e872045bfd9c465a8555bab4b8567d56a4d2d3bb)
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit f926575cd370de4052e89477582b349af5664a56)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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arch/x86/entry/calling.h | 21 +++++++++++++++++++++
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arch/x86/entry/entry_64.S | 12 ++++++------
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2 files changed, 27 insertions(+), 6 deletions(-)
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diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
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index 640aafebdc00..0b9dd8123701 100644
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--- a/arch/x86/entry/calling.h
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+++ b/arch/x86/entry/calling.h
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@@ -151,6 +151,27 @@ For 32-bit we have the following conventions - kernel is built with
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UNWIND_HINT_REGS offset=\offset extra=0
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.endm
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+ .macro POP_EXTRA_REGS
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+ popq %r15
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+ popq %r14
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+ popq %r13
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+ popq %r12
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+ popq %rbp
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+ popq %rbx
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+ .endm
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+
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+ .macro POP_C_REGS
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+ popq %r11
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+ popq %r10
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+ popq %r9
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+ popq %r8
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+ popq %rax
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+ popq %rcx
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+ popq %rdx
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+ popq %rsi
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+ popq %rdi
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+ .endm
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+
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.macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
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.if \rstor_r11
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movq 6*8(%rsp), %r11
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diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
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index 7c8258e3ad2d..a1a86e782a0e 100644
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--- a/arch/x86/entry/entry_64.S
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+++ b/arch/x86/entry/entry_64.S
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@@ -618,9 +618,9 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode)
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1:
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#endif
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SWAPGS
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- RESTORE_EXTRA_REGS
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- RESTORE_C_REGS
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- REMOVE_PT_GPREGS_FROM_STACK 8
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+ POP_EXTRA_REGS
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+ POP_C_REGS
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+ addq $8, %rsp /* skip regs->orig_ax */
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INTERRUPT_RETURN
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@@ -650,9 +650,9 @@ GLOBAL(restore_regs_and_return_to_kernel)
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ud2
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1:
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#endif
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- RESTORE_EXTRA_REGS
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- RESTORE_C_REGS
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- REMOVE_PT_GPREGS_FROM_STACK 8
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+ POP_EXTRA_REGS
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+ POP_C_REGS
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+ addq $8, %rsp /* skip regs->orig_ax */
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INTERRUPT_RETURN
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ENTRY(native_iret)
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--
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2.14.2
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