CVE-2024-43900

In the Linux kernel, the following vulnerability has been resolved:

media: xc2028: avoid use-after-free in load_firmware_cb()

syzkaller reported use-after-free in load_firmware_cb() 1. The reason is because the module allocated a struct tuner in tuner_probe(), and then the module initialization failed, the struct tuner was released. A worker which created during module initialization accesses this struct tuner later, it caused use-after-free.

The process is as follows:

task-6504 worker_thread tuner_probe <= alloc dvb_frontend [2] ... request_firmware_nowait <= create a worker ... tuner_remove <= free dvb_frontend ... request_firmware_work_func <= the firmware is ready load_firmware_cb <= but now the dvb_frontend has been freed

To fix the issue, check the dvd_frontend in load_firmware_cb(), if it is null, report a warning and just return.

BUG: KASAN: use-after-free in load_firmware_cb+0x1310/0x17a0 Read of size 8 at addr ffff8000d7ca2308 by task kworker/2:3/6504

 Call trace:
  load_firmware_cb+0x1310/0x17a0
  request_firmware_work_func+0x128/0x220
  process_one_work+0x770/0x1824
  worker_thread+0x488/0xea0
  kthread+0x300/0x430
  ret_from_fork+0x10/0x20

 Allocated by task 6504:
  kzalloc
  tuner_probe+0xb0/0x1430
  i2c_device_probe+0x92c/0xaf0
  really_probe+0x678/0xcd0
  driver_probe_device+0x280/0x370
  __device_attach_driver+0x220/0x330
  bus_for_each_drv+0x134/0x1c0
  __device_attach+0x1f4/0x410
  device_initial_probe+0x20/0x30
  bus_probe_device+0x184/0x200
  device_add+0x924/0x12c0
  device_register+0x24/0x30
  i2c_new_device+0x4e0/0xc44
  v4l2_i2c_new_subdev_board+0xbc/0x290
  v4l2_i2c_new_subdev+0xc8/0x104
  em28xx_v4l2_init+0x1dd0/0x3770...