lkml.org 
[lkml]   [2020]   [Jul]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH stable v4.9 v2] arm64: entry: Place an SB sequence following an ERET instruction
Date
From: Will Deacon <will.deacon@arm.com>

commit 679db70801da9fda91d26caf13bf5b5ccc74e8e8 upstream

Some CPUs can speculate past an ERET instruction and potentially perform
speculative accesses to memory before processing the exception return.
Since the register state is often controlled by a lower privilege level
at the point of an ERET, this could potentially be used as part of a
side-channel attack.

This patch emits an SB sequence after each ERET so that speculation is
held up on exception return.

Signed-off-by: Will Deacon <will.deacon@arm.com>
[florian: Adjust hyp-entry.S to account for the label
added change to hyp/entry.S]
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v2:

- added missing hunk in hyp/entry.S per Will's feedback

arch/arm64/kernel/entry.S | 2 ++
arch/arm64/kvm/hyp/entry.S | 2 ++
arch/arm64/kvm/hyp/hyp-entry.S | 4 ++++
3 files changed, 8 insertions(+)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index ca978d7d98eb..3408c782702c 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -255,6 +255,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
.else
eret
.endif
+ sb
.endm

.macro get_thread_info, rd
@@ -945,6 +946,7 @@ __ni_sys_trace:
mrs x30, far_el1
.endif
eret
+ sb
.endm

.align 11
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index a360ac6e89e9..93704e6894d2 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -83,6 +83,7 @@ ENTRY(__guest_enter)

// Do not touch any register after this!
eret
+ sb
ENDPROC(__guest_enter)

ENTRY(__guest_exit)
@@ -195,4 +196,5 @@ alternative_endif
ldp x0, x1, [sp], #16

eret
+ sb
ENDPROC(__fpsimd_guest_restore)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index bf4988f9dae8..3675e7f0ab72 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -97,6 +97,7 @@ el1_sync: // Guest trapped into EL2
do_el2_call

2: eret
+ sb

el1_hvc_guest:
/*
@@ -147,6 +148,7 @@ wa_epilogue:
mov x0, xzr
add sp, sp, #16
eret
+ sb

el1_trap:
get_vcpu_ptr x1, x0
@@ -198,6 +200,7 @@ el2_error:
b.ne __hyp_panic
mov x0, #(1 << ARM_EXIT_WITH_SERROR_BIT)
eret
+ sb

ENTRY(__hyp_do_panic)
mov lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
@@ -206,6 +209,7 @@ ENTRY(__hyp_do_panic)
ldr lr, =panic
msr elr_el2, lr
eret
+ sb
ENDPROC(__hyp_do_panic)

ENTRY(__hyp_panic)
--
2.17.1
\
 
 \ /
  Last update: 2020-07-09 21:53    [W:0.105 / U:1.328 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site