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Re: [libvirt] [PATCH] daemon: Fix crash in virTypedParameterArrayClear



On 2012年07月30日 22:29, Jiri Denemark wrote:
On Mon, Jul 30, 2012 at 21:08:22 +0800, Osier Yang wrote:
On 2012年07月30日 19:55, Jiri Denemark wrote:
Daemon uses the following pattern when dispatching APIs with typed
parameters:

      VIR_ALLOC_N(params, nparams);
      virDomain*(dom, params,&nparams, flags);
      virTypedParameterArrayClear(params, nparams);

In case nparams was originally set to 0, virDomain* API would fill it
with the number of typed parameters it can provide and we would use this
number (rather than zero) to clear params. Because VIR_ALLOC* returns
non-NULL pointer even if size is 0, the code would end up walking
through random memory. If we were lucky enough and the memory contained
7 (VIR_TYPED_PARAM_STRING) at the right place, we would try to free a
random pointer and crash.

Let's make sure params stays NULL when nparams is 0.
---
   daemon/remote.c | 16 ++++++++--------
   1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/daemon/remote.c b/daemon/remote.c
index 80626a2..d25717c 100644
--- a/daemon/remote.c
+++ b/daemon/remote.c
@@ -989,7 +989,7 @@ remoteDispatchDomainGetSchedulerParameters(virNetServerPtr server ATTRIBUTE_UNUS
           virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
           goto cleanup;
       }
-    if (VIR_ALLOC_N(params, nparams)<   0)
+    if (nparams&&   VIR_ALLOC_N(params, nparams)<   0)
           goto no_memory;

       if (!(dom = get_nonnull_domain(priv->conn, args->dom)))
@@ -1098,7 +1098,7 @@ remoteDispatchDomainGetSchedulerParametersFlags(virNetServerPtr server ATTRIBUTE
           virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
           goto cleanup;
       }
-    if (VIR_ALLOC_N(params, nparams)<   0)
+    if (nparams&&   VIR_ALLOC_N(params, nparams)<   0)

Isn't nparams for these 2 APIs are guarantee positive in the APIs?

virCheckPositiveArgGoto(*nparams, error);

Yes but this function is an entry point from RPC and the daemon should not
rely on client-side checking.


Makes sense, ACK.

Osier


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