From: Diana Craciun <diana.craciun@nxp.com>
Date: Fri, 27 Jul 2018 23:06:38 +0000 (+1000)
Subject: powerpc/fsl: Sanitize the syscall table for NXP PowerPC 32 bit platforms
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c28218d4abbf4f2035495334d8bfcba64bda4787;p=linux.git

powerpc/fsl: Sanitize the syscall table for NXP PowerPC 32 bit platforms

Used barrier_nospec to sanitize the syscall table.

Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 3bd097be90d92..e58c3f467db51 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -35,6 +35,7 @@
 #include <asm/export.h>
 #include <asm/asm-405.h>
 #include <asm/feature-fixups.h>
+#include <asm/barrier.h>
 
 /*
  * MSR_KERNEL is > 0x10000 on 4xx/Book-E since it include MSR_CE.
@@ -360,6 +361,15 @@ syscall_dotrace_cont:
 	ori	r10,r10,sys_call_table@l
 	slwi	r0,r0,2
 	bge-	66f
+
+	barrier_nospec_asm
+	/*
+	 * Prevent the load of the handler below (based on the user-passed
+	 * system call number) being speculatively executed until the test
+	 * against NR_syscalls and branch to .66f above has
+	 * committed.
+	 */
+
 	lwzx	r10,r10,r0	/* Fetch system call handler [ptr] */
 	mtlr	r10
 	addi	r9,r1,STACK_FRAME_OVERHEAD