[PATCH 2/2] hverkuil/go7007: staging: media: go7007: rmmod firmware protection stuff

[Volokh Konstantin <volokh84@gmail.com>]

If firmware wasn`t load, rmmod fail with oops:

usbcore: deregistering interface driver go7007
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<ffffffff81797d02>] __mutex_lock_slowpath+0xa2/0x140
PGD 13143b067 PUD 132a52067 PMD 0
Oops: 0002 [#1] SMP
Modules linked in: go7007_usb(C-) go7007(C) videobuf2_core bttv videobuf_dma_sg videobuf_core btcx_risc rc_core v4l2_common videodev videobuf2_vmalloc videobuf2_memops tveeprom
CPU 0
Pid: 3305, comm: rmmod Tainted: G         C   3.9.0-rc1+ #4 To Be Filled By O.E.M. To Be Filled By O.E.M./H55MX-S Series
RIP: 0010:[<ffffffff81797d02>]  [<ffffffff81797d02>] __mutex_lock_slowpath+0xa2/0x140
RSP: 0018:ffff88013220bd18  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff880132264c80 RCX: 00000000ffffffff
RDX: ffff88013220bd20 RSI: ffff880130d3ecc0 RDI: ffff880132264c84
RBP: ffff88013220bd68 R08: 0000000000000000 R09: ffffea0004c5c940
R10: ffffffff811a08d3 R11: 0000000000027854 R12: ffff880132264c84
R13: ffff8801325ec410 R14: 00000000ffffffff R15: ffff880132264c88
Mar 12 01:25:57 Video kernel: [  128.939419] FS:  00007fb32649d700(0000) GS:ffff880137c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000000 CR3: 0000000130f1d000 CR4: 00000000000007f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process rmmod (pid: 3305, threadinfo ffff88013220a000, task ffff8801325ec410)
Stack:
ffff88013220bd48 ffff880132264c88 0000000000000000 ffff880131abf800
ffff880130d3ecc0 ffff880132264c80 ffff880132264c80 ffff880132264478
ffff880132264000 0000000000000000 ffff88013220bd88 ffffffff81797c05
Call Trace:
 [<ffffffff81797c05>] mutex_lock+0x25/0x40
 [<ffffffffa0090051>] go7007_usb_disconnect+0x41/0xb0 [go7007_usb]
 [<ffffffff814b105b>] usb_unbind_interface+0x5b/0x130
 [<ffffffff813f0a71>] __device_release_driver+0x61/0xd0
 [<ffffffff813f1340>] driver_detach+0xb0/0xc0
 [<ffffffff813f0859>] bus_remove_driver+0x79/0xd0
 [<ffffffff813f19da>] driver_unregister+0x5a/0x90
 [<ffffffff814b0d64>] usb_deregister+0x64/0xd0
 [<ffffffffa00914dc>] go7007_usb_driver_exit+0x10/0x12 [go7007_usb]
 [<ffffffff8109370c>] sys_delete_module+0x15c/0x240
 [<ffffffff817a1d12>] system_call_fastpath+0x16/0x1b
Code: 00 4c 8d 63 04 4c 8d 7b 08 41 be ff ff ff ff 4c 89 e7 e8 92 26 00 00 48 8b 43 10 48 8d 55 b8 4c 89 7d b8 48 89 53 10 48 89 45 c0 <48> 89 10 44 89 f0 4c 89 6d c8 87 03 83 f8 01 75 1f eb 27 0f 1f
RIP  [<ffffffff81797d02>] __mutex_lock_slowpath+0xa2/0x140
RSP <ffff88013220bd18>
CR2: 0000000000000000

Signed-off-by: Volokh Konstantin <volokh84@gmail.com>
---
 drivers/staging/media/go7007/go7007-usb.c |   25 +++++++++++++------------
 1 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/staging/media/go7007/go7007-usb.c b/drivers/staging/media/go7007/go7007-usb.c
index bd23d7d..48ad01f 100644
--- a/drivers/staging/media/go7007/go7007-usb.c
+++ b/drivers/staging/media/go7007/go7007-usb.c
@@ -1316,18 +1316,19 @@ static void go7007_usb_disconnect(struct usb_interface *intf)
 {
 	struct go7007 *go = to_go7007(usb_get_intfdata(intf));
 
-	mutex_lock(&go->queue_lock);
-	mutex_lock(&go->serialize_lock);
-
-	if (go->audio_enabled)
-		go7007_snd_remove(go);
-
-	go->status = STATUS_SHUTDOWN;
-	v4l2_device_disconnect(&go->v4l2_dev);
-	video_unregister_device(&go->vdev);
-	mutex_unlock(&go->serialize_lock);
-	mutex_unlock(&go->queue_lock);
-
+	if (go->status == STATUS_ONLINE) {
+		mutex_lock(&go->queue_lock);
+		mutex_lock(&go->serialize_lock);
+
+		if (go->audio_enabled)
+			go7007_snd_remove(go);
+
+		go->status = STATUS_SHUTDOWN;
+		v4l2_device_disconnect(&go->v4l2_dev);
+		video_unregister_device(&go->vdev);
+		mutex_unlock(&go->serialize_lock);
+		mutex_unlock(&go->queue_lock);
+	}
 	v4l2_device_put(&go->v4l2_dev);
 }
 
-- 
1.7.7.6