[PATCH v2] target/ppc: Add lower bound check for watchdogNumber

Add missing lower bound check for H_WATCHDOG H_CALL's watchdogNumber parameter
as per PAPR documentation ver 12.10.00 section 14.15.5 'H_WATCHDOG'.

Closes : https://gitlab.com/qemu-project/qemu/-/work_items/3600
Signed-off-by: Chinmay Rath <[email protected]>
---

Changes from v1 : Incorporated changes suggested by Amit.
v1 : https://lore.kernel.org/qemu-devel/[email protected]/

 hw/watchdog/spapr_watchdog.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/hw/watchdog/spapr_watchdog.c b/hw/watchdog/spapr_watchdog.c
index 5b3f50de3a..460b4457a6 100644
--- a/hw/watchdog/spapr_watchdog.c
+++ b/hw/watchdog/spapr_watchdog.c
@@ -127,6 +127,12 @@ static void watchdog_expired(void *pw)
     }
 }
 
+static inline bool watchdogNumber_valid(target_ulong watchdogNumber,
+                                        SpaprMachineState *spapr)
+{
+    return watchdogNumber >= 1 && watchdogNumber <= ARRAY_SIZE(spapr->wds);
+}
+
 static target_ulong h_watchdog(PowerPCCPU *cpu,
                                SpaprMachineState *spapr,
                                target_ulong opcode, target_ulong *args)
@@ -145,7 +151,7 @@ static target_ulong h_watchdog(PowerPCCPU *cpu,
 
     switch (operation) {
     case PSERIES_WDTF_OP_START:
-        if (watchdogNumber > ARRAY_SIZE(spapr->wds)) {
+        if (!watchdogNumber_valid(watchdogNumber, spapr)) {
             return H_P2;
         }
         if (timeoutInMs <= WDT_MIN_TIMEOUT) {
@@ -170,11 +176,11 @@ static target_ulong h_watchdog(PowerPCCPU *cpu,
     case PSERIES_WDTF_OP_STOP:
         if (watchdogNumber == PSERIES_WDT_STOP_ALL) {
             ret = watchdog_stop_all(spapr);
-        } else if (watchdogNumber <= ARRAY_SIZE(spapr->wds)) {
+        } else if (!watchdogNumber_valid(watchdogNumber, spapr)) {
+            return H_P2;
+        } else {
             ret = watchdog_stop(watchdogNumber,
                                 &spapr->wds[watchdogNumber - 1]);
-        } else {
-            return H_P2;
         }
         break;
     case PSERIES_WDTF_OP_QUERY:
@@ -184,7 +190,7 @@ static target_ulong h_watchdog(PowerPCCPU *cpu,
         trace_spapr_watchdog_query(args[0]);
         break;
     case PSERIES_WDTF_OP_QUERY_LPM:
-        if (watchdogNumber > ARRAY_SIZE(spapr->wds)) {
+        if (!watchdogNumber_valid(watchdogNumber, spapr)) {
             return H_P2;
         }
         args[0] = PSERIES_WDTQL_QUERY_NOT_STOPPED;
-- 
2.55.0