mISDN: Fix null pointer dereference at mISDN_FsmNew

If mISDN_FsmNew() fails to allocate memory for jumpmatrix
then null pointer dereference will occur on any write to
jumpmatrix.

The patch adds check on successful allocation and
corresponding error handling.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Anton Vasilyev <vasilyev@ispras.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/mISDN/fsm.c

@@ -26,7 +26,7 @@
 
 #define FSM_TIMER_DEBUG 0
 
-void
+int
 mISDN_FsmNew(struct Fsm *fsm,
 	     struct FsmNode *fnlist, int fncount)
 {
@@ -34,6 +34,8 @@ mISDN_FsmNew(struct Fsm *fsm,
 
 	fsm->jumpmatrix = kzalloc(sizeof(FSMFNPTR) * fsm->state_count *
 				  fsm->event_count, GFP_KERNEL);
+	if (fsm->jumpmatrix == NULL)
+		return -ENOMEM;
 
 	for (i = 0; i < fncount; i++)
 		if ((fnlist[i].state >= fsm->state_count) ||
@@ -45,6 +47,7 @@ mISDN_FsmNew(struct Fsm *fsm,
 		} else
 			fsm->jumpmatrix[fsm->state_count * fnlist[i].event +
 					fnlist[i].state] = (FSMFNPTR) fnlist[i].routine;
+	return 0;
 }
 EXPORT_SYMBOL(mISDN_FsmNew);
 

drivers/isdn/mISDN/fsm.h

@@ -55,7 +55,7 @@ struct FsmTimer {
 	void *arg;
 };
 
-extern void mISDN_FsmNew(struct Fsm *, struct FsmNode *, int);
+extern int mISDN_FsmNew(struct Fsm *, struct FsmNode *, int);
 extern void mISDN_FsmFree(struct Fsm *);
 extern int mISDN_FsmEvent(struct FsmInst *, int , void *);
 extern void mISDN_FsmChangeState(struct FsmInst *, int);

drivers/isdn/mISDN/layer1.c

@@ -414,8 +414,7 @@ l1_init(u_int *deb)
 	l1fsm_s.event_count = L1_EVENT_COUNT;
 	l1fsm_s.strEvent = strL1Event;
 	l1fsm_s.strState = strL1SState;
-	mISDN_FsmNew(&l1fsm_s, L1SFnList, ARRAY_SIZE(L1SFnList));
-	return 0;
+	return mISDN_FsmNew(&l1fsm_s, L1SFnList, ARRAY_SIZE(L1SFnList));
 }
 
 void

drivers/isdn/mISDN/layer2.c

@@ -2247,15 +2247,26 @@ static struct Bprotocol X75SLP = {
 int
 Isdnl2_Init(u_int *deb)
 {
+	int res;
 	debug = deb;
 	mISDN_register_Bprotocol(&X75SLP);
 	l2fsm.state_count = L2_STATE_COUNT;
 	l2fsm.event_count = L2_EVENT_COUNT;
 	l2fsm.strEvent = strL2Event;
 	l2fsm.strState = strL2State;
-	mISDN_FsmNew(&l2fsm, L2FnList, ARRAY_SIZE(L2FnList));
-	TEIInit(deb);
+	res = mISDN_FsmNew(&l2fsm, L2FnList, ARRAY_SIZE(L2FnList));
+	if (res)
+		goto error;
+	res = TEIInit(deb);
+	if (res)
+		goto error_fsm;
 	return 0;
+
+error_fsm:
+	mISDN_FsmFree(&l2fsm);
+error:
+	mISDN_unregister_Bprotocol(&X75SLP);
+	return res;
 }
 
 void

drivers/isdn/mISDN/tei.c

@@ -1387,23 +1387,37 @@ create_teimanager(struct mISDNdevice *dev)
 
 int TEIInit(u_int *deb)
 {
+	int res;
 	debug = deb;
 	teifsmu.state_count = TEI_STATE_COUNT;
 	teifsmu.event_count = TEI_EVENT_COUNT;
 	teifsmu.strEvent = strTeiEvent;
 	teifsmu.strState = strTeiState;
-	mISDN_FsmNew(&teifsmu, TeiFnListUser, ARRAY_SIZE(TeiFnListUser));
+	res = mISDN_FsmNew(&teifsmu, TeiFnListUser, ARRAY_SIZE(TeiFnListUser));
+	if (res)
+		goto error;
 	teifsmn.state_count = TEI_STATE_COUNT;
 	teifsmn.event_count = TEI_EVENT_COUNT;
 	teifsmn.strEvent = strTeiEvent;
 	teifsmn.strState = strTeiState;
-	mISDN_FsmNew(&teifsmn, TeiFnListNet, ARRAY_SIZE(TeiFnListNet));
+	res = mISDN_FsmNew(&teifsmn, TeiFnListNet, ARRAY_SIZE(TeiFnListNet));
+	if (res)
+		goto error_smn;
 	deactfsm.state_count =  DEACT_STATE_COUNT;
 	deactfsm.event_count = DEACT_EVENT_COUNT;
 	deactfsm.strEvent = strDeactEvent;
 	deactfsm.strState = strDeactState;
-	mISDN_FsmNew(&deactfsm, DeactFnList, ARRAY_SIZE(DeactFnList));
+	res = mISDN_FsmNew(&deactfsm, DeactFnList, ARRAY_SIZE(DeactFnList));
+	if (res)
+		goto error_deact;
 	return 0;
+
+error_deact:
+	mISDN_FsmFree(&teifsmn);
+error_smn:
+	mISDN_FsmFree(&teifsmu);
+error:
+	return res;
 }
 
 void TEIFree(void)