"value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmedia: xc2028: avoid use-after-free in load_firmware_cb()\n\nsyzkaller reported use-after-free in load_firmware_cb() [1].\nThe reason is because the module allocated a struct tuner in tuner_probe(),\nand then the module initialization failed, the struct tuner was released.\nA worker which created during module initialization accesses this struct\ntuner later, it caused use-after-free.\n\nThe process is as follows:\n\ntask-6504 worker_thread\ntuner_probe <= alloc dvb_frontend [2]\n...\nrequest_firmware_nowait <= create a worker\n...\ntuner_remove <= free dvb_frontend\n...\n request_firmware_work_func <= the firmware is ready\n load_firmware_cb <= but now the dvb_frontend has been freed\n\nTo fix the issue, check the dvd_frontend in load_firmware_cb(), if it is\nnull, report a warning and just return.\n\n[1]:\n ==================================================================\n BUG: KASAN: use-after-free in load_firmware_cb+0x1310/0x17a0\n Read of size 8 at addr ffff8000d7ca2308 by task kworker/2:3/6504\n\n Call trace:\n load_firmware_cb+0x1310/0x17a0\n request_firmware_work_func+0x128/0x220\n process_one_work+0x770/0x1824\n worker_thread+0x488/0xea0\n kthread+0x300/0x430\n ret_from_fork+0x10/0x20\n\n Allocated by task 6504:\n kzalloc\n tuner_probe+0xb0/0x1430\n i2c_device_probe+0x92c/0xaf0\n really_probe+0x678/0xcd0\n driver_probe_device+0x280/0x370\n __device_attach_driver+0x220/0x330\n bus_for_each_drv+0x134/0x1c0\n __device_attach+0x1f4/0x410\n device_initial_probe+0x20/0x30\n bus_probe_device+0x184/0x200\n device_add+0x924/0x12c0\n device_register+0x24/0x30\n i2c_new_device+0x4e0/0xc44\n v4l2_i2c_new_subdev_board+0xbc/0x290\n v4l2_i2c_new_subdev+0xc8/0x104\n em28xx_v4l2_init+0x1dd0/0x3770\n\n Freed by task 6504:\n kfree+0x238/0x4e4\n tuner_remove+0x144/0x1c0\n i2c_device_remove+0xc8/0x290\n __device_release_driver+0x314/0x5fc\n device_release_driver+0x30/0x44\n bus_remove_device+0x244/0x490\n device_del+0x350/0x900\n device_unregister+0x28/0xd0\n i2c_unregister_device+0x174/0x1d0\n v4l2_device_unregister+0x224/0x380\n em28xx_v4l2_init+0x1d90/0x3770\n\n The buggy address belongs to the object at ffff8000d7ca2000\n which belongs to the cache kmalloc-2k of size 2048\n The buggy address is located 776 bytes inside of\n 2048-byte region [ffff8000d7ca2000, ffff8000d7ca2800)\n The buggy address belongs to the page:\n page:ffff7fe00035f280 count:1 mapcount:0 mapping:ffff8000c001f000 index:0x0\n flags: 0x7ff800000000100(slab)\n raw: 07ff800000000100 ffff7fe00049d880 0000000300000003 ffff8000c001f000\n raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000\n page dumped because: kasan: bad access detected\n\n Memory state around the buggy address:\n ffff8000d7ca2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n ffff8000d7ca2280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n >ffff8000d7ca2300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n ^\n ffff8000d7ca2380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n ffff8000d7ca2400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb\n ==================================================================\n\n[2]\n Actually, it is allocated for struct tuner, and dvb_frontend is inside."