Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH 5/8] x86,vdso: Make the PER_CPU segment 32 bits | Date | Tue, 23 Sep 2014 10:50:55 -0700 |
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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 <luto@amacapital.net> --- 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); -- 1.9.3
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