Re: [Xen-devel] [PATCH v3 2/3] x86/ldt: Make modify_ldt optional

2015-07-24 Thread Willy Tarreau
On Thu, Jul 23, 2015 at 05:09:21PM -0700, Kees Cook wrote: All this to say that probably only a handful of tricky syscalls would need an on/off switch but clearly not all of them at all, so I'd rather add a few entries just for the relevant ones, mainly to fix compatibility issues and

Re: [Xen-devel] [PATCH v3 2/3] x86/ldt: Make modify_ldt optional

2015-07-24 Thread Willy Tarreau
On Fri, Jul 24, 2015 at 09:24:51AM +0200, Willy Tarreau wrote: On Thu, Jul 23, 2015 at 05:09:21PM -0700, Kees Cook wrote: All this to say that probably only a handful of tricky syscalls would need an on/off switch but clearly not all of them at all, so I'd rather add a few entries just

Re: [Xen-devel] [PATCH v3 2/3] x86/ldt: Make modify_ldt optional

2015-07-23 Thread Willy Tarreau
On Thu, Jul 23, 2015 at 04:40:14PM -0700, Andy Lutomirski wrote: On Thu, Jul 23, 2015 at 4:36 PM, Kees Cook keesc...@chromium.org wrote: I've been pondering something like this that is even MORE generic, for any syscall. Something like a syscalls directory under /proc/sys/kernel, with 1

Re: [Xen-devel] [PATCH v3 2/3] x86/ldt: Make modify_ldt optional

2015-07-23 Thread Kees Cook
On Thu, Jul 23, 2015 at 4:58 PM, Willy Tarreau w...@1wt.eu wrote: On Thu, Jul 23, 2015 at 04:40:14PM -0700, Andy Lutomirski wrote: On Thu, Jul 23, 2015 at 4:36 PM, Kees Cook keesc...@chromium.org wrote: I've been pondering something like this that is even MORE generic, for any syscall.

Re: [Xen-devel] [PATCH v3 2/3] x86/ldt: Make modify_ldt optional

2015-07-23 Thread Andy Lutomirski
On Thu, Jul 23, 2015 at 4:36 PM, Kees Cook keesc...@chromium.org wrote: On Thu, Jul 23, 2015 at 3:24 AM, Willy Tarreau w...@1wt.eu wrote: #ifdef CONFIG_SMP static void flush_ldt(void *current_mm) { @@ -254,6 +260,9 @@ asmlinkage int sys_modify_ldt(int func, void __user *ptr, {

Re: [Xen-devel] [PATCH v3 2/3] x86/ldt: Make modify_ldt optional

2015-07-23 Thread Jan Beulich
On 22.07.15 at 21:23, l...@kernel.org wrote: --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1015,6 +1015,7 @@ config VM86 config X86_16BIT bool Enable support for 16-bit segments if EXPERT default y + depends on MODIFY_LDT_SYSCALL ---help--- This option