From: tip-bot for Dan Williams <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: torvalds@linux-foundation.org, bp@alien8.de, brgerst@gmail.com,
stable@vger.kernel.org, dan.j.williams@intel.com,
linux-kernel@vger.kernel.org, jpoimboe@redhat.com, hpa@zytor.com,
mingo@kernel.org, dvlasenk@redhat.com, peterz@infradead.org,
luto@kernel.org, tglx@linutronix.de
Subject: [tip:x86/pti] x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface
Date: Tue, 6 Feb 2018 04:00:07 -0800 [thread overview]
Message-ID: <tip-3ac6d8c787b835b997eb23e43e09aa0895ef7d58@git.kernel.org> (raw)
In-Reply-To: <151787989146.7847.15749181712358213254.stgit@dwillia2-desk3.amr.corp.intel.com>
Commit-ID: 3ac6d8c787b835b997eb23e43e09aa0895ef7d58
Gitweb: https://git.kernel.org/tip/3ac6d8c787b835b997eb23e43e09aa0895ef7d58
Author: Dan Williams <dan.j.williams@intel.com>
AuthorDate: Mon, 5 Feb 2018 17:18:11 -0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 6 Feb 2018 11:47:44 +0100
x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface
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 <ak@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: <stable@vger.kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/151787989146.7847.15749181712358213254.stgit@dwillia2-desk3.amr.corp.intel.com
[ Made small improvements to the changelog and the code comments. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/calling.h | 19 +++++++++++++++++++
arch/x86/entry/entry_64.S | 6 +++++-
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 3f48f69..f4b129d 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -147,6 +147,25 @@ For 32-bit we have the following conventions - kernel is built with
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
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 065a71b..9e48002 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -575,6 +575,7 @@ 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)
@@ -1133,6 +1134,7 @@ 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)
@@ -1178,6 +1180,7 @@ 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
@@ -1230,8 +1233,8 @@ 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
@@ -1428,6 +1431,7 @@ ENTRY(nmi)
pushq %r14 /* pt_regs->r14 */
pushq %r15 /* pt_regs->r15 */
UNWIND_HINT_REGS
+ CLEAR_REGS_NOSPEC
ENCODE_FRAME_POINTER
/*
next prev parent reply other threads:[~2018-02-06 12:06 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-06 1:18 [PATCH v3 0/3] x86/entry: Clear registers to sanitize speculative usages Dan Williams
2018-02-06 1:18 ` [PATCH v3 1/3] x86/entry: Clear extra registers beyond syscall arguments for 64bit kernels Dan Williams
2018-02-06 11:52 ` [tip:x86/pti] x86/entry/64: Clear extra registers beyond syscall arguments, to reduce speculation attack surface tip-bot for Dan Williams
2018-02-06 1:18 ` [PATCH v3 2/3] x86/entry: Clear registers for 64bit exceptions/interrupts Dan Williams
2018-02-06 9:04 ` Dominik Brodowski
2018-02-06 10:48 ` Ingo Molnar
2018-02-06 9:17 ` Dominik Brodowski
2018-02-06 10:51 ` Ingo Molnar
2018-02-06 10:57 ` Dominik Brodowski
2018-02-06 21:25 ` [PATCH tip-pti 1/2] x86/entry: remove SAVE_C_REGS_EXCEPT_* macros Dominik Brodowski
2018-02-06 22:56 ` Linus Torvalds
2018-02-06 21:32 ` [PATCH tip-pti 2/2] x86/entry: interleave XOR register clearing with PUSH/MOV instructions Dominik Brodowski
2018-02-06 22:30 ` Dan Williams
2018-02-06 22:48 ` Linus Torvalds
2018-02-06 23:05 ` Andy Lutomirski
2018-02-06 23:54 ` Andi Kleen
2018-02-07 1:30 ` Linus Torvalds
2018-02-07 15:18 ` Andi Kleen
2018-02-07 17:05 ` Linus Torvalds
2018-02-07 17:37 ` Linus Torvalds
2018-02-06 12:00 ` tip-bot for Dan Williams [this message]
2018-02-06 1:18 ` [PATCH v3 3/3] x86/entry: Clear registers for compat syscalls Dan Williams
2018-02-06 7:26 ` Ingo Molnar
2018-02-06 7:53 ` Dan Williams
2018-02-06 12:00 ` [tip:x86/pti] x86/entry/64/compat: Clear registers for compat syscalls, to reduce speculation attack surface tip-bot for Dan Williams
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