V4L/DVB: budget: Oops: "BUG: unable to handle kernel NULL pointer dereference"

Never call dvb_frontend_detach if we failed to attach a frontend. This fixes
the following oops:

[    8.172997] DVB: registering new adapter (TT-Budget S2-1600 PCI)
[    8.209018] adapter has MAC addr = 00:d0:5c:cc:a7:29
[    8.328665] Intel ICH 0000:00:1f.5: PCI INT B -> GSI 17 (level, low) -> IRQ 17
[    8.328753] Intel ICH 0000:00:1f.5: setting latency timer to 64
[    8.562047] DVB: Unable to find symbol stv090x_attach()
[    8.562117] BUG: unable to handle kernel NULL pointer dereference at 000000ac
[    8.562239] IP: [<e08b04a3>] dvb_frontend_detach+0x4/0x67 [dvb_core]

Ref http://bugs.debian.org/575207

Also clean up if we are unable to register the tuner and LNB drivers

[mchehab@redhat.com: add printk log level, to calm down chechpatch.pl]
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Reported-by: Fladischer Michael <FladischerMichael@fladi.at>
Acked-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/ttpci/budget.c

@@ -628,6 +628,7 @@ static void frontend_init(struct budget *budget)
 						 &tt1600_stv6110x_config,
 						 &budget->i2c_adap);
 
+				if (ctl) {
 					tt1600_stv090x_config.tuner_init	  = ctl->tuner_init;
 					tt1600_stv090x_config.tuner_sleep	  = ctl->tuner_sleep;
 					tt1600_stv090x_config.tuner_set_mode	  = ctl->tuner_set_mode;
@@ -646,11 +647,17 @@ static void frontend_init(struct budget *budget)
 					if (budget->dvb_frontend->ops.init)
 						budget->dvb_frontend->ops.init(budget->dvb_frontend);
 
-				dvb_attach(isl6423_attach,
+					if (dvb_attach(isl6423_attach,
 						       budget->dvb_frontend,
 						       &budget->i2c_adap,
-					&tt1600_isl6423_config);
-
+						       &tt1600_isl6423_config) == NULL) {
+						printk(KERN_ERR "%s: No Intersil ISL6423 found!\n", __func__);
+						goto error_out;
+					}
+				} else {
+					printk(KERN_ERR "%s: No STV6110(A) Silicon Tuner found!\n", __func__);
+					goto error_out;
+				}
 			}
 		}
 		break;