[PATCH] media: wl128x: Fix some error handling in fm_v4l2_init_video_device()

[Kefeng Wang]

The fm_v4l2_init_video_device() forget to unregister v4l2/video device
in the error path, it could lead to UAF issue, eg,

  BUG: KASAN: use-after-free in atomic64_read include/asm-generic/atomic-instrumented.h:836 [inline]
  BUG: KASAN: use-after-free in atomic_long_read include/asm-generic/atomic-long.h:28 [inline]
  BUG: KASAN: use-after-free in __mutex_unlock_slowpath+0x92/0x690 kernel/locking/mutex.c:1206
  Read of size 8 at addr ffff8881e84a7c70 by task v4l_id/3659

  CPU: 1 PID: 3659 Comm: v4l_id Not tainted 5.1.0 #8
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
  Call Trace:
   __dump_stack lib/dump_stack.c:77 [inline]
   dump_stack+0xa9/0x10e lib/dump_stack.c:113
   print_address_description+0x65/0x270 mm/kasan/report.c:187
   kasan_report+0x149/0x18d mm/kasan/report.c:317
   atomic64_read include/asm-generic/atomic-instrumented.h:836 [inline]
   atomic_long_read include/asm-generic/atomic-long.h:28 [inline]
   __mutex_unlock_slowpath+0x92/0x690 kernel/locking/mutex.c:1206
   fm_v4l2_fops_open+0xac/0x120 [fm_drv]
   v4l2_open+0x191/0x390 [videodev]
   chrdev_open+0x20d/0x570 fs/char_dev.c:417
   do_dentry_open+0x700/0xf30 fs/open.c:777
   do_last fs/namei.c:3416 [inline]
   path_openat+0x7c4/0x2a90 fs/namei.c:3532
   do_filp_open+0x1a5/0x2b0 fs/namei.c:3563
   do_sys_open+0x302/0x490 fs/open.c:1069
   do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  RIP: 0033:0x7f8180c17c8e
  ...
  Allocated by task 3642:
   set_track mm/kasan/common.c:87 [inline]
   __kasan_kmalloc.constprop.3+0xa0/0xd0 mm/kasan/common.c:497
   fm_drv_init+0x13/0x1000 [fm_drv]
   do_one_initcall+0xbc/0x47d init/main.c:901
   do_init_module+0x1b5/0x547 kernel/module.c:3456
   load_module+0x6405/0x8c10 kernel/module.c:3804
   __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
   do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

  Freed by task 3642:
   set_track mm/kasan/common.c:87 [inline]
   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:459
   slab_free_hook mm/slub.c:1429 [inline]
   slab_free_freelist_hook mm/slub.c:1456 [inline]
   slab_free mm/slub.c:3003 [inline]
   kfree+0xe1/0x270 mm/slub.c:3958
   fm_drv_init+0x1e6/0x1000 [fm_drv]
   do_one_initcall+0xbc/0x47d init/main.c:901
   do_init_module+0x1b5/0x547 kernel/module.c:3456
   load_module+0x6405/0x8c10 kernel/module.c:3804
   __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
   do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

Add relevant unregister functions to fix it.

Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
 drivers/media/radio/wl128x/fmdrv_v4l2.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/radio/wl128x/fmdrv_v4l2.c b/drivers/media/radio/wl128x/fmdrv_v4l2.c
index e25fd4d4d280..a1eaea19a81c 100644
--- a/drivers/media/radio/wl128x/fmdrv_v4l2.c
+++ b/drivers/media/radio/wl128x/fmdrv_v4l2.c
@@ -550,6 +550,7 @@ int fm_v4l2_init_video_device(struct fmdev *fmdev, int radio_nr)
 
 	/* Register with V4L2 subsystem as RADIO device */
 	if (video_register_device(&gradio_dev, VFL_TYPE_RADIO, radio_nr)) {
+		v4l2_device_unregister(&fmdev->v4l2_dev);
 		fmerr("Could not register video device\n");
 		return -ENOMEM;
 	}
@@ -563,6 +564,8 @@ int fm_v4l2_init_video_device(struct fmdev *fmdev, int radio_nr)
 	if (ret < 0) {
 		fmerr("(fmdev): Can't init ctrl handler\n");
 		v4l2_ctrl_handler_free(&fmdev->ctrl_handler);
+		video_unregister_device(fmdev->radio_dev);
+		v4l2_device_unregister(&fmdev->v4l2_dev);
 		return -EBUSY;
 	}
 
-- 
2.20.1