[Xen-changelog] [xen master] domctl: also pause domain for "extended" context updates

[patchbot@xxxxxxx]

commit 53f808a3880da13d0a0909f446698891a41f6869
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Feb 6 12:20:20 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Feb 6 12:20:20 2014 +0100

    domctl: also pause domain for "extended" context updates
    
    This is not just for consistency with "base" context updates, but
    actually needed so that guest side accesses can't race with control
    domain side updates.
    
    This would have been a security issue if XSA-77 hadn't waived them on
    the affected domctl operation.
    
    While looking at the code I also spotted a redundant NULL check in the
    "base" context update handling code, which is being removed.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Keir Fraser <keir@xxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Release-acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---
 xen/arch/x86/domctl.c |    7 +++++++
 xen/common/domctl.c   |    4 ----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 41cfd7c..432a180 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -853,6 +853,8 @@ long arch_do_domctl(
         }
         else
         {
+            if ( d == current->domain ) /* no domain_pause() */
+                break;
             ret = -EINVAL;
             if ( evc->size < offsetof(typeof(*evc), vmce) )
                 break;
@@ -861,6 +863,7 @@ long arch_do_domctl(
                 if ( !is_canonical_address(evc->sysenter_callback_eip) ||
                      !is_canonical_address(evc->syscall32_callback_eip) )
                     break;
+                domain_pause(d);
                 fixup_guest_code_selector(d, evc->sysenter_callback_cs);
                 v->arch.pv_vcpu.sysenter_callback_cs      =
                     evc->sysenter_callback_cs;
@@ -881,6 +884,8 @@ long arch_do_domctl(
                       (evc->syscall32_callback_cs & ~3) ||
                       evc->syscall32_callback_eip )
                 break;
+            else
+                domain_pause(d);
 
             BUILD_BUG_ON(offsetof(struct xen_domctl_ext_vcpucontext,
                                   mcg_cap) !=
@@ -899,6 +904,8 @@ long arch_do_domctl(
             }
             else
                 ret = 0;
+
+            domain_unpause(d);
         }
     }
     break;
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 904d27b..f237be4 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -334,10 +334,6 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         unsigned int vcpu = op->u.vcpucontext.vcpu;
         struct vcpu *v;
 
-        ret = -ESRCH;
-        if ( d == NULL )
-            break;
-
         ret = -EINVAL;
         if ( (d == current->domain) || /* no domain_pause() */
              (vcpu >= d->max_vcpus) || ((v = d->vcpu[vcpu]) == NULL) )
--
generated by git-patchbot for /home/xen/git/xen.git#master

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