From: Suraj Jitindar Singh <surajjs@amazon.com>
To: <stable@vger.kernel.org>
Cc: <surajjs@amazon.com>, <sjitindarsingh@gmail.com>,
<cascardo@canonical.com>, <kvm@vger.kernel.org>,
<pbonzini@redhat.com>, <jpoimboe@kernel.org>,
<peterz@infradead.org>, <x86@kernel.org>
Subject: [PATCH 4.14 19/34] x86/speculation: Add LFENCE to RSB fill sequence
Date: Thu, 27 Oct 2022 13:55:11 -0700 [thread overview]
Message-ID: <20221027205512.17684-3-surajjs@amazon.com> (raw)
In-Reply-To: <20221027205512.17684-1-surajjs@amazon.com>
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
commit ba6e31af2be96c4d0536f2152ed6f7b6c11bca47 upstream.
RSB fill sequence does not have any protection for miss-prediction of
conditional branch at the end of the sequence. CPU can speculatively
execute code immediately after the sequence, while RSB filling hasn't
completed yet.
#define __FILL_RETURN_BUFFER(reg, nr, sp) \
mov $(nr/2), reg; \
771: \
ANNOTATE_INTRA_FUNCTION_CALL; \
call 772f; \
773: /* speculation trap */ \
UNWIND_HINT_EMPTY; \
pause; \
lfence; \
jmp 773b; \
772: \
ANNOTATE_INTRA_FUNCTION_CALL; \
call 774f; \
775: /* speculation trap */ \
UNWIND_HINT_EMPTY; \
pause; \
lfence; \
jmp 775b; \
774: \
add $(BITS_PER_LONG/8) * 2, sp; \
dec reg; \
jnz 771b; <----- CPU can miss-predict here.
Before RSB is filled, RETs that come in program order after this macro
can be executed speculatively, making them vulnerable to RSB-based
attacks.
Mitigate it by adding an LFENCE after the conditional branch to prevent
speculation while RSB is being filled.
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/nospec-branch.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 652c1159a6f6..0d474525caec 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -54,7 +54,9 @@
774: \
add $(BITS_PER_LONG/8) * 2, sp; \
dec reg; \
- jnz 771b;
+ jnz 771b; \
+ /* barrier for jnz misprediction */ \
+ lfence;
#ifdef __ASSEMBLY__
--
2.17.1
next prev parent reply other threads:[~2022-10-27 21:03 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-27 20:48 [PATCH 4.14 00/34] Retbleed & PBRSB Mitigations Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 01/34] Revert "x86/cpu: Add a steppings field to struct x86_cpu_id" Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 02/34] x86/cpufeature: Add facility to check for min microcode revisions Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 03/34] x86/cpufeature: Fix various quality problems in the <asm/cpu_device_hd.h> header Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 04/34] x86/devicetable: Move x86 specific macro out of generic code Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 05/34] x86/cpu: Add consistent CPU match macros Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 06/34] x86/cpu: Add a steppings field to struct x86_cpu_id Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 07/34] x86/entry: Remove skip_r11rcx Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 08/34] x86/cpufeatures: Move RETPOLINE flags to word 11 Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 09/34] x86/bugs: Report AMD retbleed vulnerability Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 10/34] x86/bugs: Add AMD retbleed= boot parameter Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 11/34] x86/bugs: Keep a per-CPU IA32_SPEC_CTRL value Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 12/34] x86/entry: Add kernel IBRS implementation Suraj Jitindar Singh
2022-10-27 20:54 ` [PATCH 4.14 13/34] x86/bugs: Optimize SPEC_CTRL MSR writes Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 14/34] x86/speculation: Add spectre_v2=ibrs option to support Kernel IBRS Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 15/34] x86/bugs: Split spectre_v2_select_mitigation() and spectre_v2_user_select_mitigation() Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 16/34] x86/bugs: Report Intel retbleed vulnerability Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 17/34] entel_idle: Disable IBRS during long idle Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 18/34] x86/speculation: Change FILL_RETURN_BUFFER to work with objtool Suraj Jitindar Singh
2022-10-27 20:55 ` Suraj Jitindar Singh [this message]
2022-10-27 20:55 ` [PATCH 4.14 20/34] x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 21/34] x86/speculation: Fix firmware entry SPEC_CTRL handling Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 22/34] x86/speculation: Fix SPEC_CTRL write on SMT state change Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 23/34] x86/speculation: Use cached host SPEC_CTRL value for guest entry/exit Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 24/34] x86/speculation: Remove x86_spec_ctrl_mask Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 25/34] KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 26/34] KVM: VMX: Fix IBRS handling after vmexit Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 27/34] x86/speculation: Fill RSB on vmexit for IBRS Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 28/34] x86/common: Stamp out the stepping madness Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 29/34] x86/cpu/amd: Enumerate BTC_NO Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 30/34] x86/bugs: Add Cannon lake to RETBleed affected CPU list Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 31/34] x86/speculation: Disable RRSBA behavior Suraj Jitindar Singh
2022-10-27 20:55 ` [PATCH 4.14 32/34] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current Suraj Jitindar Singh
2022-10-27 20:56 ` [PATCH 4.14 33/34] x86/bugs: Warn when "ibrs" mitigation is selected on Enhanced IBRS parts Suraj Jitindar Singh
2022-10-27 20:56 ` [PATCH 4.14 34/34] x86/speculation: Add RSB VM Exit protections Suraj Jitindar Singh
2022-10-31 7:00 ` [PATCH 4.14 00/34] Retbleed & PBRSB Mitigations Greg KH
-- strict thread matches above, loose matches on Subject: below --
2022-10-31 7:02 [PATCH 4.14 00/34] 4.14.297-rc1 review Greg Kroah-Hartman
2022-10-31 7:02 ` [PATCH 4.14 19/34] x86/speculation: Add LFENCE to RSB fill sequence Greg Kroah-Hartman
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