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Commit 287e0131 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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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: default avatarAndy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/179f490d659307873eefd09206bebd417e2ab5ad.1411494540.git.luto@amacapital.net


Signed-off-by: default avatarIngo 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);