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Re: [PATCH 14/14] hw/i386/vmport: Assert vmport initialized before regis

From: Liran Alon
Subject: Re: [PATCH 14/14] hw/i386/vmport: Assert vmport initialized before registering commands
Date: Tue, 10 Mar 2020 12:57:26 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

On 10/03/2020 11:30, Michael S. Tsirkin wrote:
On Tue, Mar 10, 2020 at 01:54:11AM +0200, Liran Alon wrote:
vmport_register() is also called from other modules such as vmmouse.
Therefore, these modules rely that vmport is realized before those call
sites. If this is violated, vmport_register() will NULL-deref.

To make such issues easier to debug, assert in vmport_register() that
vmport is already realized.

Reviewed-by: Nikita Leshenko <address@hidden>
Signed-off-by: Liran Alon <address@hidden>

Hmm and what does actually make sure it is realized?

port_state global var is only set in vmport_realizefn().


  hw/i386/vmport.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/hw/i386/vmport.c b/hw/i386/vmport.c
index 95d4a23ce9ba..659a323e8448 100644
--- a/hw/i386/vmport.c
+++ b/hw/i386/vmport.c
@@ -68,6 +68,8 @@ static VMPortState *port_state;
  void vmport_register(VMPortCommand command, VMPortReadFunc *func, void 
      assert(command < VMPORT_ENTRIES);
+    assert(port_state);
      trace_vmport_register(command, func, opaque);
      port_state->func[command] = func;
      port_state->opaque[command] = opaque;

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