KVM ARM Archive on lore.kernel.org
 help / color / Atom feed
From: Florian Fainelli <f.fainelli@gmail.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Fangrui Song <maskray@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	open list <linux-kernel@vger.kernel.org>,
	stable@vger.kernel.org,
	"open list:KERNEL VIRTUAL MACHINE FOR ARM64 KVM/arm64"
	<kvmarm@lists.cs.columbia.edu>, Mark Brown <broonie@kernel.org>,
	Kristina Martsenko <kristina.martsenko@arm.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH stable v4.9 v2] arm64: entry: Place an SB sequence following an ERET instruction
Date: Thu,  9 Jul 2020 12:50:23 -0700
Message-ID: <20200709195034.15185-1-f.fainelli@gmail.com> (raw)

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

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

             reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-09 19:50 Florian Fainelli [this message]
2020-07-11  0:28 ` Sasha Levin
2020-07-20 13:04 ` Greg KH
2020-07-20 18:26   ` Florian Fainelli
2020-08-06 20:00     ` Florian Fainelli
2020-08-07 13:14       ` Greg KH
2020-08-07 18:17         ` Florian Fainelli
2020-08-13 20:52           ` Florian Fainelli
2020-08-21 16:03         ` Will Deacon
2020-08-21 17:16           ` Florian Fainelli
2020-08-24 16:32             ` Will Deacon
2020-08-24 16:42               ` Florian Fainelli

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200709195034.15185-1-f.fainelli@gmail.com \
    --to=f.fainelli@gmail.com \
    --cc=ardb@kernel.org \
    --cc=broonie@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=kristina.martsenko@arm.com \
    --cc=kvmarm@lists.cs.columbia.edu \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=maskray@google.com \
    --cc=maz@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=samitolvanen@google.com \
    --cc=stable@vger.kernel.org \
    --cc=will.deacon@arm.com \
    --cc=will@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM ARM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvmarm/0 kvmarm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvmarm kvmarm/ https://lore.kernel.org/kvmarm \
		kvmarm@lists.cs.columbia.edu
	public-inbox-index kvmarm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/edu.columbia.cs.lists.kvmarm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git