From: Andy Lutomirski Date: Tue, 23 Sep 2014 17:50:55 +0000 (-0700) Subject: x86/vdso: Make the PER_CPU segment 32 bits X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=287e013108a104e459e675432cf20087feab2b67;p=linux-beck.git 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 --- 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);