[Xen-changelog] [xen-unstable] Do not allow HVM save/restore of a dying domain.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1215015052 -3600
# Node ID 3a40a6997cc0610a17136fd38da1d0a1f94d932b
# Parent  b3d827e63a09d8d54b5bea688c2bb5d953d1464f
Do not allow HVM save/restore of a dying domain.

It's not a sensible thing to do, and it is easier than auditing all
state save/restore functions for safety (most importantly, racing
against domain_relinquish_resources).

Also place a spin_barrier on domain_lock after asserting d->is_dying,
allowing critical regions under the domain_lock to safely check
is_dying and avoid races with domain_relinquish_resources().

Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/common/domain.c   |    1 +
 xen/common/hvm/save.c |    6 ++++++
 2 files changed, 7 insertions(+)

diff -r b3d827e63a09 -r 3a40a6997cc0 xen/common/domain.c
--- a/xen/common/domain.c       Wed Jul 02 13:54:20 2008 +0100
+++ b/xen/common/domain.c       Wed Jul 02 17:10:52 2008 +0100
@@ -341,6 +341,7 @@ int domain_kill(struct domain *d)
     case DOMDYING_alive:
         domain_pause(d);
         d->is_dying = DOMDYING_dying;
+        spin_barrier(&d->domain_lock);
         evtchn_destroy(d);
         gnttab_release_mappings(d);
         /* fallthrough */
diff -r b3d827e63a09 -r 3a40a6997cc0 xen/common/hvm/save.c
--- a/xen/common/hvm/save.c     Wed Jul 02 13:54:20 2008 +0100
+++ b/xen/common/hvm/save.c     Wed Jul 02 17:10:52 2008 +0100
@@ -84,6 +84,9 @@ int hvm_save(struct domain *d, hvm_domai
     hvm_save_handler handler;
     uint16_t i;
 
+    if ( d->is_dying )
+        return -EINVAL;
+
     hdr.magic = HVM_FILE_MAGIC;
     hdr.version = HVM_FILE_VERSION;
 
@@ -140,6 +143,9 @@ int hvm_load(struct domain *d, hvm_domai
     hvm_load_handler handler;
     struct vcpu *v;
     
+    if ( d->is_dying )
+        return -EINVAL;
+
     /* Read the save header, which must be first */
     if ( hvm_load_entry(HEADER, h, &hdr) != 0 ) 
         return -1;

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