Re: [PATCH v3 1/3] xen: fix XEN_DOMCTL_gdbsx_guestmemio crash

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.04.2022 15:52, Juergen Gross wrote:
> A hypervisor built without CONFIG_GDBSX will crash in case the
> XEN_DOMCTL_gdbsx_guestmemio domctl is being called, as the call will
> end up in iommu_do_domctl() with d == NULL:
> 
> (XEN) CPU:    6
> (XEN) RIP:    e008:[<ffff82d040269984>] iommu_do_domctl+0x4/0x30
> (XEN) RFLAGS: 0000000000010202   CONTEXT: hypervisor (d0v0)
> (XEN) rax: 00000000000003e8   rbx: ffff830856277ef8   rcx: ffff830856277fff
> ...
> (XEN) Xen call trace:
> (XEN)    [<ffff82d040269984>] R iommu_do_domctl+0x4/0x30
> (XEN)    [<ffff82d04035cd5f>] S arch_do_domctl+0x7f/0x2330
> (XEN)    [<ffff82d040239e46>] S do_domctl+0xe56/0x1930
> (XEN)    [<ffff82d040238ff0>] S do_domctl+0/0x1930
> (XEN)    [<ffff82d0402f8c59>] S pv_hypercall+0x99/0x110
> (XEN)    [<ffff82d0402f5161>] S 
> arch/x86/pv/domain.c#_toggle_guest_pt+0x11/0x90
> (XEN)    [<ffff82d040366288>] S lstar_enter+0x128/0x130
> (XEN)
> (XEN) Pagetable walk from 0000000000000144:
> (XEN)  L4[0x000] = 0000000000000000 ffffffffffffffff
> (XEN)
> (XEN) ****************************************
> (XEN) Panic on CPU 6:
> (XEN) FATAL PAGE FAULT
> (XEN) [error_code=0000]
> (XEN) Faulting linear address: 0000000000000144
> 
> Fix this issue by making sure the domain pointer has a sane value.
> 
> Reported-by: Cheyenne Wills <cheyenne.wills@xxxxxxxxx>
> Fixes: e726a82ca0dc ("xen: make gdbsx support configurable")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>