[PATCH 2/3] Revert "UBUNTU: SAUCE: bpf: Use barrier_nospec() instead of osb()"

[Tyler Hicks]

This reverts commit 5b9ee25974f7e54c94e8b2ef307d9830d714f490 which was
part of an out-of-tree mitigation for CVE-2017-5753 (Spectre variant 1),
in the BPF subsystem, that was available at the time of the coordinated
release date. The Ubuntu kernel has since rebased on top of newer
linux-stable releases and picked up commit b2157399cc98 ("bpf: prevent
out-of-bounds speculation") which is upstream's mitigation of Spectre
variant 1 in the BPF code.

CVE-2017-5753

Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---
 kernel/bpf/core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 89e4f17b2c4d..2d77df1a22c9 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -27,9 +27,9 @@
 #include <linux/random.h>
 #include <linux/moduleloader.h>
 #include <linux/bpf.h>
-#include <linux/nospec.h>
 
 #include <asm/unaligned.h>
+#include <asm/barrier.h>
 
 /* Registers */
 #define BPF_R0	regs[BPF_REG_0]
@@ -632,7 +632,7 @@ select_insn:
 		DST = IMM;
 		CONT;
 	LD_IMM_DW:
-		barrier_nospec();
+		osb();
 		DST = (u64) (u32) insn[0].imm | ((u64) (u32) insn[1].imm) << 32;
 		insn++;
 		CONT;
@@ -847,7 +847,7 @@ out:
 		*(SIZE *)(unsigned long) (DST + insn->off) = IMM;	\
 		CONT;							\
 	LDX_MEM_##SIZEOP:						\
-		barrier_nospec();					\
+		osb();							\
 		DST = *(SIZE *)(unsigned long) (SRC + insn->off);	\
 		CONT;
 
-- 
2.7.4