[Qemu-devel] [FIX v1 PATCH] spapr_rtas: Prevent QEMU crash during hotplug without a prior device_add

[Qemu-devel] [FIX v1 PATCH] spapr_rtas: Prevent QEMU crash during hotplug without a prior device_add

[Bharata B Rao]

If drmgr is used in the guest to hotplug a device before a device_add
has been issued via the QEMU monitor, QEMU segfaults in configure_connector
call. This occurs due to accessing of NULL FDT which otherwise would have
been created and associated with the DRC during device_add command.

Check for NULL FDT and return failure from configure_connector call.
As per PAPR+, an error value of -9003 seems appropriate for this failure.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
---
Changes in v1:
 - Use error value of -9003 instead of RTAS_OUT_HW_ERROR.

v0: http://lists.nongnu.org/archive/html/qemu-devel/2015-08/msg03026.html

 hw/ppc/spapr_rtas.c        |  6 ++++++
 include/hw/ppc/spapr_drc.h | 15 ++++++++-------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index e99e25f..3b7b20b 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -522,6 +522,12 @@ static void rtas_ibm_configure_connector(PowerPCCPU *cpu,
 
     drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
     fdt = drck->get_fdt(drc, NULL);
+    if (!fdt) {
+        DPRINTF("rtas_ibm_configure_connector: Missing FDT for DRC index: %xh\n",
+                drc_index);
+        rc = SPAPR_DR_CC_RESPONSE_NOT_CONFIGURABLE;
+        goto out;
+    }
 
     ccs = spapr_ccs_find(spapr, drc_index);
     if (!ccs) {
diff --git a/include/hw/ppc/spapr_drc.h b/include/hw/ppc/spapr_drc.h
index 60cda35..28ffeae 100644
--- a/include/hw/ppc/spapr_drc.h
+++ b/include/hw/ppc/spapr_drc.h
@@ -119,13 +119,14 @@ typedef enum {
 } sPAPRDREntitySense;
 
 typedef enum {
-    SPAPR_DR_CC_RESPONSE_NEXT_SIB       = 1, /* currently unused */
-    SPAPR_DR_CC_RESPONSE_NEXT_CHILD     = 2,
-    SPAPR_DR_CC_RESPONSE_NEXT_PROPERTY  = 3,
-    SPAPR_DR_CC_RESPONSE_PREV_PARENT    = 4,
-    SPAPR_DR_CC_RESPONSE_SUCCESS        = 0,
-    SPAPR_DR_CC_RESPONSE_ERROR          = -1,
-    SPAPR_DR_CC_RESPONSE_CONTINUE       = -2,
+    SPAPR_DR_CC_RESPONSE_NEXT_SIB         = 1, /* currently unused */
+    SPAPR_DR_CC_RESPONSE_NEXT_CHILD       = 2,
+    SPAPR_DR_CC_RESPONSE_NEXT_PROPERTY    = 3,
+    SPAPR_DR_CC_RESPONSE_PREV_PARENT      = 4,
+    SPAPR_DR_CC_RESPONSE_SUCCESS          = 0,
+    SPAPR_DR_CC_RESPONSE_ERROR            = -1,
+    SPAPR_DR_CC_RESPONSE_CONTINUE         = -2,
+    SPAPR_DR_CC_RESPONSE_NOT_CONFIGURABLE = -9003,
 } sPAPRDRCCResponse;
 
 typedef void (spapr_drc_detach_cb)(DeviceState *d, void *opaque);
-- 
2.1.0

Re: [Qemu-devel] [FIX v1 PATCH] spapr_rtas: Prevent QEMU crash during hotplug without a prior device_add

[David Gibson]

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On Mon, Aug 31, 2015 at 11:08:13AM +0530, Bharata B Rao wrote:
> If drmgr is used in the guest to hotplug a device before a device_add
> has been issued via the QEMU monitor, QEMU segfaults in configure_connector
> call. This occurs due to accessing of NULL FDT which otherwise would have
> been created and associated with the DRC during device_add command.
> 
> Check for NULL FDT and return failure from configure_connector call.
> As per PAPR+, an error value of -9003 seems appropriate for this failure.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> Cc: Michael Roth <mdroth@linux.vnet.ibm.com>

Applied to spapr-next, thanks.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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