From: Will Deacon <will.deacon@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com, ard.biesheuvel@linaro.org,
marc.zyngier@arm.com, lorenzo.pieralisi@arm.com,
christoffer.dall@linaro.org, linux-kernel@vger.kernel.org,
shankerd@codeaurora.org, jnair@caviumnetworks.com,
Will Deacon <will.deacon@arm.com>
Subject: [PATCH v3 01/13] arm64: use RET instruction for exiting the trampoline
Date: Mon, 8 Jan 2018 17:32:26 +0000 [thread overview]
Message-ID: <1515432758-26440-2-git-send-email-will.deacon@arm.com> (raw)
In-Reply-To: <1515432758-26440-1-git-send-email-will.deacon@arm.com>
Speculation attacks against the entry trampoline can potentially resteer
the speculative instruction stream through the indirect branch and into
arbitrary gadgets within the kernel.
This patch defends against these attacks by forcing a misprediction
through the return stack: a dummy BL instruction loads an entry into
the stack, so that the predicted program flow of the subsequent RET
instruction is to a branch-to-self instruction which is finally resolved
as a branch to the kernel vectors with speculation suppressed.
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/arm64/kernel/entry.S | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 031392ee5f47..6ceed4877daf 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1029,6 +1029,14 @@ alternative_else_nop_endif
.if \regsize == 64
msr tpidrro_el0, x30 // Restored in kernel_ventry
.endif
+ /*
+ * Defend against branch aliasing attacks by pushing a dummy
+ * entry onto the return stack and using a RET instruction to
+ * enter the full-fat kernel vectors.
+ */
+ bl 2f
+ b .
+2:
tramp_map_kernel x30
#ifdef CONFIG_RANDOMIZE_BASE
adr x30, tramp_vectors + PAGE_SIZE
@@ -1041,7 +1049,7 @@ alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
msr vbar_el1, x30
add x30, x30, #(1b - tramp_vectors)
isb
- br x30
+ ret
.endm
.macro tramp_exit, regsize = 64
--
2.1.4
next prev parent reply other threads:[~2018-01-08 17:32 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-08 17:32 [PATCH v3 00/13] arm64 kpti hardening and variant 2 workarounds Will Deacon
2018-01-08 17:32 ` Will Deacon [this message]
2018-01-08 17:32 ` [PATCH v3 02/13] arm64: Kconfig: Reword UNMAP_KERNEL_AT_EL0 kconfig entry Will Deacon
2018-01-09 17:17 ` Christoph Hellwig
2018-01-10 19:26 ` Will Deacon
2018-01-08 17:32 ` [PATCH v3 03/13] arm64: Take into account ID_AA64PFR0_EL1.CSV3 Will Deacon
2018-01-08 17:32 ` [PATCH v3 04/13] arm64: cpufeature: Pass capability structure to ->enable callback Will Deacon
2018-01-08 17:32 ` [PATCH v3 05/13] drivers/firmware: Expose psci_get_version through psci_ops structure Will Deacon
2018-01-08 17:32 ` [PATCH v3 06/13] arm64: Move post_ttbr_update_workaround to C code Will Deacon
2018-01-08 17:32 ` [PATCH v3 07/13] arm64: Add skeleton to harden the branch predictor against aliasing attacks Will Deacon
2018-01-09 12:55 ` Philippe Ombredanne
2018-01-08 17:32 ` [PATCH v3 08/13] arm64: KVM: Use per-CPU vector when BP hardening is enabled Will Deacon
2018-01-08 17:32 ` [PATCH v3 09/13] arm64: KVM: Make PSCI_VERSION a fast path Will Deacon
2018-01-08 17:32 ` [PATCH v3 10/13] arm64: cputype: Add missing MIDR values for Cortex-A72 and Cortex-A75 Will Deacon
2018-01-08 17:32 ` [PATCH v3 11/13] arm64: Implement branch predictor hardening for affected Cortex-A CPUs Will Deacon
2018-01-09 16:12 ` Suzuki K Poulose
2018-01-15 11:51 ` Marc Zyngier
2018-01-15 18:01 ` Catalin Marinas
2018-01-08 17:32 ` [PATCH v3 12/13] arm64: Implement branch predictor hardening for Falkor Will Deacon
2018-01-12 17:58 ` Shanker Donthineni
2018-01-08 17:32 ` [PATCH v3 13/13] arm64: cputype: Add MIDR values for Cavium ThunderX2 CPUs Will Deacon
2018-01-08 18:53 ` [PATCH v3 00/13] arm64 kpti hardening and variant 2 workarounds Catalin Marinas
2018-01-09 14:07 ` Matthias Brugger
2018-01-12 15:58 ` Catalin Marinas
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