[Xen-devel] [PATCH] libxc: Protect xc_domain_resume from clobbering domain registers

[Jason Andryuk <andryuk@xxxxxxxx>]

xc_domain_resume() expects the guest to be in state SHUTDOWN_suspend.
However, nothing verifies the state before modify_returncode() modifies
the domain's registers.  This will crash guest processes or the kernel
itself.

This can be demonstrated with `LIBXL_SAVE_HELPER=/bin/false xl migrate`.

Signed-off-by: Jason Andryuk <andryuk@xxxxxxxx>
---
Changes since RFC:
 - Return -1 from modify_returncode
 - Set errno to EINVAL
---
 tools/libxc/xc_resume.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/libxc/xc_resume.c b/tools/libxc/xc_resume.c
index 18b4818..2163ad9 100644
--- a/tools/libxc/xc_resume.c
+++ b/tools/libxc/xc_resume.c
@@ -39,6 +39,13 @@ static int modify_returncode(xc_interface *xch, uint32_t 
domid)
         return -1;
     }
 
+    if ( !info.shutdown || (info.shutdown_reason != SHUTDOWN_suspend) )
+    {
+        ERROR("Domain not in suspended state");
+        errno = EINVAL;
+        return -1;
+    }
+
     if ( info.hvm )
     {
         /* HVM guests without PV drivers have no return code to modify. */
-- 
1.8.3.1


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