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

@@ -628,29 +628,36 @@ static void frontend_init(struct budget *budget)
 						 &tt1600_stv6110x_config,
 						 &budget->i2c_adap);
 
-				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;
-				tt1600_stv090x_config.tuner_set_frequency = ctl->tuner_set_frequency;
-				tt1600_stv090x_config.tuner_get_frequency = ctl->tuner_get_frequency;
-				tt1600_stv090x_config.tuner_set_bandwidth = ctl->tuner_set_bandwidth;
-				tt1600_stv090x_config.tuner_get_bandwidth = ctl->tuner_get_bandwidth;
-				tt1600_stv090x_config.tuner_set_bbgain	  = ctl->tuner_set_bbgain;
-				tt1600_stv090x_config.tuner_get_bbgain	  = ctl->tuner_get_bbgain;
-				tt1600_stv090x_config.tuner_set_refclk	  = ctl->tuner_set_refclk;
-				tt1600_stv090x_config.tuner_get_status	  = ctl->tuner_get_status;
-
-				/* call the init function once to initialize
-				   tuner's clock output divider and demod's
-				   master clock */
-				if (budget->dvb_frontend->ops.init)
-					budget->dvb_frontend->ops.init(budget->dvb_frontend);
-
-				dvb_attach(isl6423_attach,
-					budget->dvb_frontend,
-					&budget->i2c_adap,
-					&tt1600_isl6423_config);
-
+				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;
+					tt1600_stv090x_config.tuner_set_frequency = ctl->tuner_set_frequency;
+					tt1600_stv090x_config.tuner_get_frequency = ctl->tuner_get_frequency;
+					tt1600_stv090x_config.tuner_set_bandwidth = ctl->tuner_set_bandwidth;
+					tt1600_stv090x_config.tuner_get_bandwidth = ctl->tuner_get_bandwidth;
+					tt1600_stv090x_config.tuner_set_bbgain	  = ctl->tuner_set_bbgain;
+					tt1600_stv090x_config.tuner_get_bbgain	  = ctl->tuner_get_bbgain;
+					tt1600_stv090x_config.tuner_set_refclk	  = ctl->tuner_set_refclk;
+					tt1600_stv090x_config.tuner_get_status	  = ctl->tuner_get_status;
+
+					/* call the init function once to initialize
+					   tuner's clock output divider and demod's
+					   master clock */
+					if (budget->dvb_frontend->ops.init)
+						budget->dvb_frontend->ops.init(budget->dvb_frontend);
+
+					if (dvb_attach(isl6423_attach,
+						       budget->dvb_frontend,
+						       &budget->i2c_adap,
+						       &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;