Commit 51fbc055 authored Jan 03, 2015 by Daniel Borkmann Committed by Greg Kroah-Hartman Jan 27, 2015

x86, um: actually mark system call tables readonly



commit b485342bd79af363c77ef1a421c4a0aef2de9812 upstream.

Commit a074335a ("x86, um: Mark system call tables readonly") was
supposed to mark the sys_call_table in UML as RO by adding the const,
but it doesn't have the desired effect as it's nevertheless being placed
into the data section since __cacheline_aligned enforces sys_call_table
being placed into .data..cacheline_aligned instead. We need to use
the ____cacheline_aligned version instead to fix this issue.

Before:

$ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table"
                 U sys_writev
0000000000000000 D sys_call_table
0000000000000000 D syscall_table_size

After:

$ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table"
                 U sys_writev
0000000000000000 R sys_call_table
0000000000000000 D syscall_table_size

Fixes: a074335a ("x86, um: Mark system call tables readonly")
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent b9d078ca

arch/x86/um/sys_call_table_32.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -34,7 +34,7 @@ typedef asmlinkage void (*sys_call_ptr_t)(void);

		extern asmlinkage void sys_ni_syscall(void);

		const sys_call_ptr_t sys_call_table[] __cacheline_aligned = {
		const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
		/*
		* Smells like a compiler bug -- it doesn't work
		* when the & below is removed.

arch/x86/um/sys_call_table_64.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -46,7 +46,7 @@ typedef void (*sys_call_ptr_t)(void);

		extern void sys_ni_syscall(void);

		const sys_call_ptr_t sys_call_table[] __cacheline_aligned = {
		const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
		/*
		* Smells like a compiler bug -- it doesn't work
		* when the & below is removed.