From 287e013108a104e459e675432cf20087feab2b67 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 23 Sep 2014 10:50:55 -0700 Subject: [PATCH] x86/vdso: Make the PER_CPU segment 32 bits IMO users ought not to be able to use 16-bit segments without using modify_ldt. Fortunately, it's impossible to break espfix64 by loading the PER_CPU segment into SS because it's PER_CPU is marked read-only and SS cannot contain an RO segment, but marking PER_CPU as 32-bit is less fragile. Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/179f490d659307873eefd09206bebd417e2ab5ad.1411494540.git.luto@amacapital.net Signed-off-by: Ingo Molnar --- arch/x86/vdso/vma.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c index 0c7997467be0..32ca60c8157b 100644 --- a/arch/x86/vdso/vma.c +++ b/arch/x86/vdso/vma.c @@ -268,6 +268,7 @@ static void vsyscall_set_cpu(int cpu) .dpl = 3, /* Visible to user code */ .s = 1, /* Not a system segment */ .p = 1, /* Present */ + .d = 1, /* 32-bit */ }; write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S); -- 2.34.1