[Xen-devel,v3,01/13] xen/arm: domain: Zero the per-vCPU cpu_info

Message ID 20180612113643.32020-2-julien.grall@arm.com
State New
Headers show
  • xen/arm: SSBD (aka Spectre-v4) mitigation (XSA-263)
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Commit Message

Julien Grall June 12, 2018, 11:36 a.m.
A stack is allocated per vCPU to be used by Xen. The allocation is done
with alloc_xenheap_pages that does not zero the memory returned. However
the top of the stack is containing information that will be used to
store the initial state of the vCPU (see struct cpu_info). Some of the
fields may not be initialized and will lead to use/leak bits of previous
memory in some cases on the first run of vCPU (AFAICT this only happen on
vCPU0 for Dom0).

This is part of XSA-263.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

    Changes in v3:
        - Add stefano's reviewed-by

    Changes in v2:
        - Zero only cpu_info
 xen/arch/arm/domain.c | 1 +
 1 file changed, 1 insertion(+)


diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index ec0f042bf7..5a2a9a6b83 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -550,6 +550,7 @@  int vcpu_initialise(struct vcpu *v)
     v->arch.cpu_info = (struct cpu_info *)(v->arch.stack
                                            + STACK_SIZE
                                            - sizeof(struct cpu_info));
+    memset(v->arch.cpu_info, 0, sizeof(*v->arch.cpu_info));
     memset(&v->arch.saved_context, 0, sizeof(v->arch.saved_context));
     v->arch.saved_context.sp = (register_t)v->arch.cpu_info;