[PATCH v2 2/8] s390/sclp: check sccb len before filling in data

[Collin Walling]

The SCCB must be checked for a sufficient length before it is filled
with any data. If the length is insufficient, then the SCLP command
is suppressed and the proper response code is set in the SCCB header.

Fixes: 832be0d8a3bb ("s390x: sclp: Report insufficient SCCB length")
Signed-off-by: Collin Walling <wall...@linux.ibm.com>
---
 hw/s390x/sclp.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index 61e2e2839c..2bd618515e 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -75,6 +75,11 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
     int rnsize, rnmax;
     IplParameterBlock *ipib = s390_ipl_get_iplb();
 
+    if (be16_to_cpu(sccb->h.length) < (sizeof(ReadInfo) + cpu_count * 
sizeof(CPUEntry))) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
+        return;
+    }
+
     /* CPU information */
     prepare_cpu_entries(machine, read_info->entries, &cpu_count);
     read_info->entries_cpu = cpu_to_be16(cpu_count);
@@ -83,12 +88,6 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
 
     read_info->ibc_val = cpu_to_be32(s390_get_ibc_val());
 
-    if (be16_to_cpu(sccb->h.length) <
-            (sizeof(ReadInfo) + cpu_count * sizeof(CPUEntry))) {
-        sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
-        return;
-    }
-
     /* Configuration Characteristic (Extension) */
     s390_get_feat_block(S390_FEAT_TYPE_SCLP_CONF_CHAR,
                          read_info->conf_char);
@@ -135,17 +134,16 @@ static void sclp_read_cpu_info(SCLPDevice *sclp, SCCB 
*sccb)
     ReadCpuInfo *cpu_info = (ReadCpuInfo *) sccb;
     int cpu_count;
 
+    if (be16_to_cpu(sccb->h.length) < (sizeof(ReadCpuInfo) + cpu_count * 
sizeof(CPUEntry))) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
+        return;
+    }
+
     prepare_cpu_entries(machine, cpu_info->entries, &cpu_count);
     cpu_info->nr_configured = cpu_to_be16(cpu_count);
     cpu_info->offset_configured = cpu_to_be16(offsetof(ReadCpuInfo, entries));
     cpu_info->nr_standby = cpu_to_be16(0);
 
-    if (be16_to_cpu(sccb->h.length) <
-            (sizeof(ReadCpuInfo) + cpu_count * sizeof(CPUEntry))) {
-        sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
-        return;
-    }
-
     /* The standby offset is 16-byte for each CPU */
     cpu_info->offset_standby = cpu_to_be16(cpu_info->offset_configured
         + cpu_info->nr_configured*sizeof(CPUEntry));
-- 
2.21.3