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* [PATCH v7 00/11] Retpoline: Avoid speculative indirect calls in kernel
@ 2018-01-09 14:43 David Woodhouse
  2018-01-09 14:43 ` [PATCH v7 01/11] x86/retpoline: Add initial retpoline support David Woodhouse
                   ` (10 more replies)
  0 siblings, 11 replies; 65+ messages in thread
From: David Woodhouse @ 2018-01-09 14:43 UTC (permalink / raw)
  To: Andi Kleen
  Cc: Paul Turner, LKML, Linus Torvalds, Greg Kroah-Hartman, Tim Chen,
	Dave Hansen, tglx, Kees Cook, Rik van Riel, Peter Zijlstra,
	Andy Lutomirski, Jiri Kosina, gnomes, x86

This is a mitigation for the 'variant 2' attack described in
https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html

Using GCC patches available from the hjl/indirect/gcc-7-branch/master
branch of https://github.com/hjl-tools/gcc/commits/hjl and by manually
patching assembler code, all vulnerable indirect branches (that occur
after userspace first runs) are eliminated from the kernel.

They are replaced with a 'retpoline' call sequence which deliberately
prevents speculation.

Fedora 27 packages of the updated compiler are available at
https://koji.fedoraproject.org/koji/taskinfo?taskID=24065739


v1: Initial post.
v2: Add CONFIG_RETPOLINE to build kernel without it.
    Change warning messages.
    Hide modpost warning message
v3: Update to the latest CET-capable retpoline version
    Reinstate ALTERNATIVE support
v4: Finish reconciling Andi's and my patch sets, bug fixes.
    Exclude objtool support for now
    Add 'noretpoline' boot option
    Add AMD retpoline alternative
v5: Silence MODVERSIONS warnings
    Use pause;jmp loop instead of lfence;jmp
    Switch to X86_FEATURE_RETPOLINE positive feature logic
    Emit thunks inline from assembler macros
    Merge AMD support into initial patch
v6: Update to latest GCC patches with no dots in symbols
    Fix MODVERSIONS properly(ish)
    Fix typo breaking 32-bit, introduced in V5
    Never set X86_FEATURE_RETPOLINE_AMD yet, pending confirmation
v7: Further bikeshedding on macro names
    Stuff RSB on kernel entry
    Implement 'spectre_v2=' command line option for IBRS/IBPB too
    Revert to precisely the asm sequences from the Google paper

Andi Kleen (3):
  x86/retpoline: Temporarily disable objtool when CONFIG_RETPOLINE=y
  x86/retpoline/irq32: Convert assembler indirect jumps
  x86/retpoline: Avoid return buffer underflows on context switch

David Woodhouse (8):
  x86/retpoline: Add initial retpoline support
  x86/spectre: Add boot time option to select Spectre v2 mitigation
  x86/retpoline/crypto: Convert crypto assembler indirect jumps
  x86/retpoline/entry: Convert entry assembler indirect jumps
  x86/retpoline/ftrace: Convert ftrace assembler indirect jumps
  x86/retpoline/hyperv: Convert assembler indirect jumps
  x86/retpoline/xen: Convert Xen hypercall indirect jumps
  x86/retpoline/checksum32: Convert assembler indirect jumps

 Documentation/admin-guide/kernel-parameters.txt |  28 +++++
 arch/x86/Kconfig                                |  17 ++-
 arch/x86/Kconfig.debug                          |   6 +-
 arch/x86/Makefile                               |  10 ++
 arch/x86/crypto/aesni-intel_asm.S               |   5 +-
 arch/x86/crypto/camellia-aesni-avx-asm_64.S     |   3 +-
 arch/x86/crypto/camellia-aesni-avx2-asm_64.S    |   3 +-
 arch/x86/crypto/crc32c-pcl-intel-asm_64.S       |   3 +-
 arch/x86/entry/entry_32.S                       |  22 +++-
 arch/x86/entry/entry_64.S                       |  29 ++++-
 arch/x86/include/asm/asm-prototypes.h           |  25 ++++
 arch/x86/include/asm/cpufeatures.h              |   2 +
 arch/x86/include/asm/mshyperv.h                 |  18 +--
 arch/x86/include/asm/nospec-branch.h            | 158 ++++++++++++++++++++++++
 arch/x86/include/asm/xen/hypercall.h            |   5 +-
 arch/x86/kernel/cpu/bugs.c                      | 122 +++++++++++++++++-
 arch/x86/kernel/ftrace_32.S                     |   6 +-
 arch/x86/kernel/ftrace_64.S                     |   8 +-
 arch/x86/kernel/irq_32.c                        |   9 +-
 arch/x86/kernel/setup.c                         |   3 +
 arch/x86/lib/Makefile                           |   1 +
 arch/x86/lib/checksum_32.S                      |   7 +-
 arch/x86/lib/retpoline.S                        |  48 +++++++
 23 files changed, 499 insertions(+), 39 deletions(-)
 create mode 100644 arch/x86/include/asm/nospec-branch.h
 create mode 100644 arch/x86/lib/retpoline.S

-- 
2.7.4

^ permalink raw reply	[flat|nested] 65+ messages in thread
* [PATCH v8 06/12] x86/retpoline/entry: Convert entry assembler indirect jumps
@ 2018-01-11 21:46 David Woodhouse
  2018-01-11 23:24 ` [tip:x86/pti] " tip-bot for David Woodhouse
  0 siblings, 1 reply; 65+ messages in thread
From: David Woodhouse @ 2018-01-11 21:46 UTC (permalink / raw)
  To: Andi Kleen
  Cc: Paul Turner, LKML, Linus Torvalds, Greg Kroah-Hartman, Tim Chen,
	Dave Hansen, tglx, Kees Cook, Rik van Riel, Peter Zijlstra,
	Andy Lutomirski, Jiri Kosina, gnomes, x86, thomas.lendacky,
	Josh Poimboeuf

Convert indirect jumps in core 32/64bit entry assembler code to use
non-speculative sequences when CONFIG_RETPOLINE is enabled.

Don't use CALL_NOSPEC in entry_SYSCALL_64_fastpath because the return
address after the 'call' instruction must be *precisely* at the
.Lentry_SYSCALL_64_after_fastpath label for stub_ptregs_64 to work,
and the use of alternatives will mess that up unless we play horrid
games to prepend with NOPs and make the variants the same length. It's
not worth it; in the case where we ALTERNATIVE out the retpoline, the
first instruction at __x86.indirect_thunk.rax is going to be a bare
jmp *%rax anyway.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: https://lkml.kernel.org/r/1515508997-6154-6-git-send-email-dwmw@amazon.co.uk
---
 arch/x86/entry/entry_32.S |  5 +++--
 arch/x86/entry/entry_64.S | 12 +++++++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index ace8f32..a1f28a5 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -44,6 +44,7 @@
 #include <asm/asm.h>
 #include <asm/smap.h>
 #include <asm/frame.h>
+#include <asm/nospec-branch.h>
 
 	.section .entry.text, "ax"
 
@@ -290,7 +291,7 @@ ENTRY(ret_from_fork)
 
 	/* kernel thread */
 1:	movl	%edi, %eax
-	call	*%ebx
+	CALL_NOSPEC %ebx
 	/*
 	 * A kernel thread is allowed to return here after successfully
 	 * calling do_execve().  Exit to userspace to complete the execve()
@@ -919,7 +920,7 @@ common_exception:
 	movl	%ecx, %es
 	TRACE_IRQS_OFF
 	movl	%esp, %eax			# pt_regs pointer
-	call	*%edi
+	CALL_NOSPEC %edi
 	jmp	ret_from_exception
 END(common_exception)
 
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index ed31d00..59874bc 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -37,6 +37,7 @@
 #include <asm/pgtable_types.h>
 #include <asm/export.h>
 #include <asm/frame.h>
+#include <asm/nospec-branch.h>
 #include <linux/err.h>
 
 #include "calling.h"
@@ -187,7 +188,7 @@ ENTRY(entry_SYSCALL_64_trampoline)
 	 */
 	pushq	%rdi
 	movq	$entry_SYSCALL_64_stage2, %rdi
-	jmp	*%rdi
+	JMP_NOSPEC %rdi
 END(entry_SYSCALL_64_trampoline)
 
 	.popsection
@@ -266,7 +267,12 @@ entry_SYSCALL_64_fastpath:
 	 * It might end up jumping to the slow path.  If it jumps, RAX
 	 * and all argument registers are clobbered.
 	 */
+#ifdef CONFIG_RETPOLINE
+	movq	sys_call_table(, %rax, 8), %rax
+	call	__x86_indirect_thunk_rax
+#else
 	call	*sys_call_table(, %rax, 8)
+#endif
 .Lentry_SYSCALL_64_after_fastpath_call:
 
 	movq	%rax, RAX(%rsp)
@@ -438,7 +444,7 @@ ENTRY(stub_ptregs_64)
 	jmp	entry_SYSCALL64_slow_path
 
 1:
-	jmp	*%rax				/* Called from C */
+	JMP_NOSPEC %rax				/* Called from C */
 END(stub_ptregs_64)
 
 .macro ptregs_stub func
@@ -517,7 +523,7 @@ ENTRY(ret_from_fork)
 1:
 	/* kernel thread */
 	movq	%r12, %rdi
-	call	*%rbx
+	CALL_NOSPEC %rbx
 	/*
 	 * A kernel thread is allowed to return here after successfully
 	 * calling do_execve().  Exit to userspace to complete the execve()
-- 
2.7.4

^ permalink raw reply	[flat|nested] 65+ messages in thread

end of thread, other threads:[~2018-01-11 23:29 UTC | newest]

Thread overview: 65+ messages (download: mbox.gz / follow: Atom feed)
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2018-01-09 14:43 [PATCH v7 00/11] Retpoline: Avoid speculative indirect calls in kernel David Woodhouse
2018-01-09 14:43 ` [PATCH v7 01/11] x86/retpoline: Add initial retpoline support David Woodhouse
2018-01-09 15:55   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-10 17:34   ` tip-bot for David Woodhouse
2018-01-10 18:13   ` tip-bot for David Woodhouse
2018-01-10 18:40   ` tip-bot for David Woodhouse
2018-01-09 14:43 ` [PATCH v7 02/11] x86/retpoline: Temporarily disable objtool when CONFIG_RETPOLINE=y David Woodhouse
2018-01-09 15:56   ` [tip:x86/pti] " tip-bot for Andi Kleen
2018-01-10  5:58   ` [PATCH v7 02/11] " Josh Poimboeuf
2018-01-10 10:12     ` Peter Zijlstra
2018-01-10 17:34   ` [tip:x86/pti] " tip-bot for Andi Kleen
2018-01-10 18:13   ` tip-bot for Andi Kleen
2018-01-10 18:40   ` tip-bot for Andi Kleen
2018-01-09 14:43 ` [PATCH v7 03/11] x86/spectre: Add boot time option to select Spectre v2 mitigation David Woodhouse
2018-01-09 15:56   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-10 17:35   ` tip-bot for David Woodhouse
2018-01-10 18:03     ` Tom Lendacky
2018-01-10 18:06       ` Thomas Gleixner
2018-01-10 18:10         ` Thomas Gleixner
2018-01-10 18:14   ` tip-bot for David Woodhouse
2018-01-10 18:33     ` Tom Lendacky
2018-01-10 18:35       ` Thomas Gleixner
2018-01-10 18:41   ` tip-bot for David Woodhouse
2018-01-09 14:43 ` [PATCH v7 04/11] x86/retpoline/crypto: Convert crypto assembler indirect jumps David Woodhouse
2018-01-09 15:56   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-10 17:35   ` tip-bot for David Woodhouse
2018-01-10 18:14   ` tip-bot for David Woodhouse
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2018-01-09 14:43 ` [PATCH v7 05/11] x86/retpoline/entry: Convert entry " David Woodhouse
2018-01-09 15:57   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-10  3:54   ` [v7, 05/11] " Andrei Vagin
2018-01-10  4:30     ` Andi Kleen
2018-01-10  4:39       ` Dave Hansen
2018-01-10  5:23         ` Andrei Vagin
2018-01-10 17:36   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-10 18:15   ` tip-bot for David Woodhouse
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2018-01-09 14:43 ` [PATCH v7 06/11] x86/retpoline/ftrace: Convert ftrace " David Woodhouse
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2018-01-09 14:43 ` [PATCH v7 07/11] x86/retpoline/hyperv: Convert " David Woodhouse
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2018-01-09 14:43 ` [PATCH v7 08/11] x86/retpoline/xen: Convert Xen hypercall " David Woodhouse
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2018-01-09 14:43 ` [PATCH v7 09/11] x86/retpoline/checksum32: Convert assembler " David Woodhouse
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2018-01-09 14:43 ` [PATCH v7 10/11] x86/retpoline/irq32: " David Woodhouse
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2018-01-09 14:43 ` [PATCH v7 11/11] x86/retpoline: Avoid return buffer underflows on context switch David Woodhouse
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2018-01-11 21:46 [PATCH v8 06/12] x86/retpoline/entry: Convert entry assembler indirect jumps David Woodhouse
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