From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Elena Reshetova <elena.reshetova@intel.com>
Date: Mon, 4 Sep 2017 13:11:44 +0300
Subject: [PATCH] bpf: prevent speculative execution in eBPF interpreter
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CVE-2017-5753
CVE-2017-5715

This adds a generic memory barrier before LD_IMM_DW and
LDX_MEM_B/H/W/DW eBPF instructions during eBPF program
execution in order to prevent speculative execution on out
of bound BFP_MAP array indexes. This way an arbitary kernel
memory is not exposed through side channel attacks.

For more details, please see this Google Project Zero report: tbd

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit dd13f73106c260dea7a689d33d1457639af820aa)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 kernel/bpf/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 9a1bed1f3029..3f83c60e3e86 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -33,6 +33,7 @@
 #include <linux/rcupdate.h>
 
 #include <asm/unaligned.h>
+#include <asm/barrier.h>
 
 /* Registers */
 #define BPF_R0	regs[BPF_REG_0]
@@ -920,6 +921,7 @@ static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn,
 		DST = IMM;
 		CONT;
 	LD_IMM_DW:
+		gmb();
 		DST = (u64) (u32) insn[0].imm | ((u64) (u32) insn[1].imm) << 32;
 		insn++;
 		CONT;
@@ -1133,6 +1135,7 @@ static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn,
 		*(SIZE *)(unsigned long) (DST + insn->off) = IMM;	\
 		CONT;							\
 	LDX_MEM_##SIZEOP:						\
+		gmb();							\
 		DST = *(SIZE *)(unsigned long) (SRC + insn->off);	\
 		CONT;
 
-- 
2.14.2

