Commit 287e0131 authored Sep 23, 2014 by Andy Lutomirski Committed by Ingo Molnar Oct 28, 2014

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 <luto@amacapital.net>
Link: http://lkml.kernel.org/r/179f490d659307873eefd09206bebd417e2ab5ad.1411494540.git.luto@amacapital.net

Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 9c0080ef

arch/x86/vdso/vma.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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);