[PATCH stable v4.14 14/32] powerpc/fsl: Sanitize the syscall table for NXP PowerPC 32 bit platforms

[Michael Ellerman]

From: Diana Craciun <diana.craciun at nxp.com>

commit c28218d4abbf4f2035495334d8bfcba64bda4787 upstream.

Used barrier_nospec to sanitize the syscall table.

Signed-off-by: Diana Craciun <diana.craciun at nxp.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
---
 arch/powerpc/kernel/entry_32.S | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 4ae464b9d490..a2999cd73a82 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -33,6 +33,7 @@
 #include <asm/unistd.h>
 #include <asm/ptrace.h>
 #include <asm/export.h>
+#include <asm/barrier.h>
 
 /*
  * MSR_KERNEL is > 0x10000 on 4xx/Book-E since it include MSR_CE.
@@ -358,6 +359,15 @@ _GLOBAL(DoSyscall)
 	ori	r10,r10,sys_call_table at 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
-- 
2.20.1