Whilst attempting to crash an apparently wedged Windows domain using
'xen-hvmcrash' I managed to trigger the following ASSERT:
(XEN) Assertion '!vp->ptr' failed at viridian.c:607
with stack:
(XEN) [<ffff82d08032c55d>] viridian_map_guest_page+0x1b4/0x1b6
(XEN) [<ffff82d08032b1db>] viridian_synic_load_vcpu_ctxt+0x39/0x3b
(XEN) [<ffff82d08032b90d>] viridian.c#viridian_load_vcpu_ctxt+0x93/0xcc
(XEN) [<ffff82d0803096d6>] hvm_load+0x10e/0x19e
(XEN) [<ffff82d080274c6d>] arch_do_domctl+0xb74/0x25b4
(XEN) [<ffff82d0802068ab>] do_domctl+0x16f7/0x19d8
This happened because viridian_map_guest_page() was not written to cope
with being called multiple times, but this is unfortunately exactly what
happens when xen-hvmcrash re-loads the domain context (having clobbered
the values of RIP).
This patch simply makes viridian_map_guest_page() return immediately if it
finds the page already mapped (i.e. vp->ptr != NULL).
Signed-off-by: Paul Durrant <paul.durr...@citrix.com>
---
Cc: Jan Beulich <jbeul...@suse.com>
Cc: Andrew Cooper <andrew.coop...@citrix.com>
Cc: Wei Liu <wei.l...@citrix.com>
Cc: "Roger Pau Monné" <roger....@citrix.com>
v2:
- Stop leaking page references
---
xen/arch/x86/hvm/viridian/viridian.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/xen/arch/x86/hvm/viridian/viridian.c
b/xen/arch/x86/hvm/viridian/viridian.c
index 7d73f41de6..c78b2918d9 100644
--- a/xen/arch/x86/hvm/viridian/viridian.c
+++ b/xen/arch/x86/hvm/viridian/viridian.c
@@ -602,10 +602,12 @@ void viridian_map_guest_page(struct vcpu *v, struct
viridian_page *vp)
{
struct domain *d = v->domain;
unsigned long gmfn = vp->msr.fields.pfn;
- struct page_info *page = get_page_from_gfn(d, gmfn, NULL, P2M_ALLOC);
+ struct page_info *page;
- ASSERT(!vp->ptr);
+ if ( vp->ptr )
+ return;
+ page = get_page_from_gfn(d, gmfn, NULL, P2M_ALLOC);
if ( !page )
goto fail;
--
2.11.0
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