isdn: mISDN: correctly handle ph_info allocation failure in hfcsusb_ph_info

Modify return type of hfcusb_ph_info to int, so that we can pass error
value up the call stack when allocation of ph_info fails. Also change
three of four call sites to actually account for the memory failure.
The fourth, in ph_state_nt, is infeasible to change as it is in turn
called by ph_state which is used as a function pointer argument to
mISDN_initdchannel, which would necessitate changing its signature
and updating all the places where it is used (too many).

Fixes original flawed commit (38d2265980) from the University of
Minnesota.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210503115736.2104747-48-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/isdn/hardware/mISDN/hfcsusb.c

@@ -46,7 +46,7 @@ static void hfcsusb_start_endpoint(struct hfcsusb *hw, int channel);
 static void hfcsusb_stop_endpoint(struct hfcsusb *hw, int channel);
 static int  hfcsusb_setup_bch(struct bchannel *bch, int protocol);
 static void deactivate_bchannel(struct bchannel *bch);
-static void hfcsusb_ph_info(struct hfcsusb *hw);
+static int  hfcsusb_ph_info(struct hfcsusb *hw);
 
 /* start next background transfer for control channel */
 static void
@@ -241,7 +241,7 @@ hfcusb_l2l1B(struct mISDNchannel *ch, struct sk_buff *skb)
  * send full D/B channel status information
  * as MPH_INFORMATION_IND
  */
-static void
+static int
 hfcsusb_ph_info(struct hfcsusb *hw)
 {
 	struct ph_info *phi;
@@ -249,6 +249,9 @@ hfcsusb_ph_info(struct hfcsusb *hw)
 	int i;
 
 	phi = kzalloc(struct_size(phi, bch, dch->dev.nrbchan), GFP_ATOMIC);
+	if (!phi)
+		return -ENOMEM;
+
 	phi->dch.ch.protocol = hw->protocol;
 	phi->dch.ch.Flags = dch->Flags;
 	phi->dch.state = dch->state;
@@ -260,6 +263,8 @@ hfcsusb_ph_info(struct hfcsusb *hw)
 	_queue_data(&dch->dev.D, MPH_INFORMATION_IND, MISDN_ID_ANY,
 		    struct_size(phi, bch, dch->dev.nrbchan), phi, GFP_ATOMIC);
 	kfree(phi);
+
+	return 0;
 }
 
 /*
@@ -344,8 +349,7 @@ hfcusb_l2l1D(struct mISDNchannel *ch, struct sk_buff *skb)
 			ret = l1_event(dch->l1, hh->prim);
 		break;
 	case MPH_INFORMATION_REQ:
-		hfcsusb_ph_info(hw);
+		ret = hfcsusb_ph_info(hw);
-		ret = 0;
 		break;
 	}
 
@@ -400,8 +404,7 @@ hfc_l1callback(struct dchannel *dch, u_int cmd)
 			       hw->name, __func__, cmd);
 		return -1;
 	}
-	hfcsusb_ph_info(hw);
+	return hfcsusb_ph_info(hw);
-	return 0;
 }
 
 static int
@@ -743,8 +746,7 @@ hfcsusb_setup_bch(struct bchannel *bch, int protocol)
 			handle_led(hw, (bch->nr == 1) ? LED_B1_OFF :
 				   LED_B2_OFF);
 	}
-	hfcsusb_ph_info(hw);
+	return hfcsusb_ph_info(hw);
-	return 0;
 }
 
 static void