From 54a6a043fb8580d5a741774669ef6049f402f228 Mon Sep 17 00:00:00 2001
From: Anton Vasilyev <vasilyev@ispras.ru>
Date: Fri, 11 Aug 2017 15:57:22 +0300
Subject: [PATCH] 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    |  5 ++++-
 drivers/isdn/mISDN/fsm.h    |  2 +-
 drivers/isdn/mISDN/layer1.c |  3 +--
 drivers/isdn/mISDN/layer2.c | 15 +++++++++++++--
 drivers/isdn/mISDN/tei.c    | 20 +++++++++++++++++---
 5 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/drivers/isdn/mISDN/fsm.c b/drivers/isdn/mISDN/fsm.c
index 78fc5d5e9051..92e6570b1143 100644
--- a/drivers/isdn/mISDN/fsm.c
+++ b/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);
 
diff --git a/drivers/isdn/mISDN/fsm.h b/drivers/isdn/mISDN/fsm.h
index 928f5be192c1..e1def8490221 100644
--- a/drivers/isdn/mISDN/fsm.h
+++ b/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);
diff --git a/drivers/isdn/mISDN/layer1.c b/drivers/isdn/mISDN/layer1.c
index bebc57b72138..3192b0eb3944 100644
--- a/drivers/isdn/mISDN/layer1.c
+++ b/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
diff --git a/drivers/isdn/mISDN/layer2.c b/drivers/isdn/mISDN/layer2.c
index 7243a6746f8b..9ff0903a0e89 100644
--- a/drivers/isdn/mISDN/layer2.c
+++ b/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
diff --git a/drivers/isdn/mISDN/tei.c b/drivers/isdn/mISDN/tei.c
index 908127efccf8..12d9e5f4beb1 100644
--- a/drivers/isdn/mISDN/tei.c
+++ b/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)
-- 
2.20.1