[PATCH 4.4] vsyscall: Fix permissions for emulate mode with KAISER/PTI

Ben Hutchings
2018-01-26T16:23:10Z

The backport of KAISER to 4.4 turned vsyscall emulate mode into native
mode. Add a vsyscall_pgprot variable to hold the correct page
protections, like Borislav and Hugh did for 3.2 and 3.18.

Cc: Borislav Petkov <bp@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
---
I think this is also needed for 4.9 but haven't tested there.

Ben.

arch/x86/entry/vsyscall/vsyscall_64.c | 7 ++++---
arch/x86/include/asm/vsyscall.h | 1 +
arch/x86/mm/kaiser.c | 2 +-
3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 112178b401a1..2d359991a273 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -46,6 +46,7 @@ static enum { EMULATE, NATIVE, NONE } vsyscall_mode =
#else
EMULATE;
#endif
+unsigned long vsyscall_pgprot = __PAGE_KERNEL_VSYSCALL;

static int __init vsyscall_setup(char *str)
{
@@ -336,11 +337,11 @@ void __init map_vsyscall(void)
extern char __vsyscall_page;
unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);

+ if (vsyscall_mode != NATIVE)
+ vsyscall_pgprot = __PAGE_KERNEL_VVAR;
if (vsyscall_mode != NONE)
__set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
- vsyscall_mode == NATIVE
- ? PAGE_KERNEL_VSYSCALL
- : PAGE_KERNEL_VVAR);
+ __pgprot(vsyscall_pgprot));

BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=
(unsigned long)VSYSCALL_ADDR);
diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index 4865e10dbb55..9ee85066f407 100644
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -13,6 +13,7 @@ extern void map_vsyscall(void);
*/
extern bool emulate_vsyscall(struct pt_regs *regs, unsigned long address);
extern bool vsyscall_enabled(void);
+extern unsigned long vsyscall_pgprot;
#else
static inline void map_vsyscall(void) {}
static inline bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c
index 8af98513d36c..2298434f7bdb 100644
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -345,7 +345,7 @@ void __init kaiser_init(void)
if (vsyscall_enabled())
kaiser_add_user_map_early((void *)VSYSCALL_ADDR,
PAGE_SIZE,
- __PAGE_KERNEL_VSYSCALL);
+ vsyscall_pgprot);

for_each_possible_cpu(cpu) {
void *percpu_vaddr = __per_cpu_user_mapped_start +
--
2.15.0.rc0