This is a note to let you know that I've just added the patch titled
x86/xen: init %gs very early to avoid page faults with stack protector
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: x86-xen-init-gs-very-early-to-avoid-page-faults-with-stack-protector.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 4f277295e54c5b7340e48efea3fc5cc21a2872b7 Mon Sep 17 00:00:00 2001
From: Juergen Gross jgross@suse.com Date: Thu, 1 Feb 2018 13:40:19 +0100 Subject: x86/xen: init %gs very early to avoid page faults with stack protector
From: Juergen Gross jgross@suse.com
commit 4f277295e54c5b7340e48efea3fc5cc21a2872b7 upstream.
When running as Xen pv guest %gs is initialized some time after C code is started. Depending on stack protector usage this might be too late, resulting in page faults.
So setup %gs and MSR_GS_BASE in assembly code already.
Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross jgross@suse.com Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Tested-by: Chris Patterson cjp256@gmail.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/xen/xen-head.S | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
--- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -9,7 +9,9 @@
#include <asm/boot.h> #include <asm/asm.h> +#include <asm/msr.h> #include <asm/page_types.h> +#include <asm/percpu.h> #include <asm/unwind_hints.h>
#include <xen/interface/elfnote.h> @@ -35,6 +37,20 @@ ENTRY(startup_xen) mov %_ASM_SI, xen_start_info mov $init_thread_union+THREAD_SIZE, %_ASM_SP
+#ifdef CONFIG_X86_64 + /* Set up %gs. + * + * The base of %gs always points to the bottom of the irqstack + * union. If the stack protector canary is enabled, it is + * located at %gs:40. Note that, on SMP, the boot cpu uses + * init data section till per cpu areas are set up. + */ + movl $MSR_GS_BASE,%ecx + movq $INIT_PER_CPU_VAR(irq_stack_union),%rax + cdq + wrmsr +#endif + jmp xen_start_kernel END(startup_xen) __FINIT
Patches currently in stable-queue which might be from jgross@suse.com are
queue-4.14/x86-xen-init-gs-very-early-to-avoid-page-faults-with-stack-protector.patch