[4.6-rc1/rc2][snd_usb_audio] regression: BUG usb_audio_probe+0x2ca/0x9a0

[Shawn Starr]

Hello kernel devs,

USB audio devices broke:


[   13.873279] BUG: unable to handle kernel NULL pointer dereference at 0000000000000014 
[   13.874701] IP: [<ffffffffc0840a4a>] usb_audio_probe+0x2ca/0x9a0 [snd_usb_audio] 
[   13.876050] *PGD 0 * 
[   13.876942] Oops*: 0000 [#1] SMP * 
[   13.877896] Modules linked in*: snd_usb_audio(+) mac80211 videobuf2_vmalloc vfat irqbypass videobuf2_memops fat crct10dif_pclmul videob*
 
[   13.884695] * tpm soundcore i2c_designware_core i2c_i801 wmi dell_rbtn rfkill dell_smo8800 nfsd auth_rpcgss nfs_acl lockd grace sunrpc *
 
[   13.888261] CPU*: 7 PID: 628 Comm: systemd-udevd Not tainted 4.6.0-rc2 #1* 
[   13.889507] Hardware name*: Dell Inc. Precision M6800/05NG6V, BIOS A16 12/01/2015* 
[   13.890794] task*: ffff8807fdc61d80 ti: ffff8808074d4000 task.ti: ffff8808074d4000* 
[   13.892094] RIP*: 0010:[<ffffffffc0840a4a>]  [<ffffffffc0840a4a>] usb_audio_probe+0x2ca/0x9a0 [snd_usb_audio]* 
[   13.893543] RSP*: 0018:ffff8808074d7a80  EFLAGS: 00010246* 
[   13.894769] RAX*: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000* 
[   13.896051] RDX*: ffff8808082b2b80 RSI: 0000000000000000 RDI: ffff880807ec6880* 
[   13.897347] RBP*: ffff8808074d7af8 R08: 000000000001a6c0 R09: ffffffff813cf33c* 
[   13.898616] R10*: ffffea001ff91a00 R11: ffff8807fe2b7871 R12: ffff8807fdd3a900* 
[   13.899907] R13*: 0000000000000002 R14: ffff8807fdd3a954 R15: ffff88080748fd12* 
[   13.901205] FS*:  00007fba7d6ae8c0(0000) GS:ffff88082ddc0000(0000) knlGS:0000000000000000* 
[   13.902827] CS*:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033* 
[   13.904091] CR2*: 0000000000000014 CR3: 0000000807e7f000 CR4: 00000000001406e0* 
[   13.905398] *Stack:* 
[   13.906448] * ffff8807fedaacc8 0000000000000000 ffff8807feecac00 ffff8807fedaacc8* 
[   13.907784] * 0000000000000246 ffff8808074d7ab8 ffff8807ff1d3000 3634304253550282* 
[   13.909115] * ff00343461303a64 00000000e52cf258 ffff8807fecd5098 ffff8807fecd5000* 
[   13.910710] *Call Trace:* 
[   13.912339] * [<ffffffff815acf8d>] usb_probe_interface+0x1bd/0x300* 
[   13.913581] * [<ffffffff8150a93c>] driver_probe_device+0x22c/0x440* 
[   13.914838] * [<ffffffff8150ac21>] __driver_attach+0xd1/0xf0* 
[   13.916099] * [<ffffffff8150ab50>] ? driver_probe_device+0x440/0x440* 
[   13.917396] * [<ffffffff8150828c>] bus_for_each_dev+0x6c/0xc0* 
[   13.918660] * [<ffffffff8150a01e>] driver_attach+0x1e/0x20* 
[   13.919822] * [<ffffffff81509abb>] bus_add_driver+0x1eb/0x280* 
[   13.921074] * [<ffffffff8150b550>] driver_register+0x60/0xe0* 
[   13.921085] * [<ffffffff815ab834>] usb_register_driver+0x84/0x140* 
[   13.921086] * [<ffffffffc086d000>] ? 0xffffffffc086d000* 
[   13.921091] * [<ffffffffc086d01e>] usb_audio_driver_init+0x1e/0x1000 [snd_usb_audio]* 
[   13.921095] * [<ffffffff81002123>] do_one_initcall+0xb3/0x200* 
[   13.921096] * [<ffffffff811fa371>] ? __vunmap+0x81/0xd0* 
[   13.921098] * [<ffffffff81219ac9>] ? kmem_cache_alloc_trace+0x189/0x1f0* 
[   13.921099] * [<ffffffff8121b11b>] ? kfree+0x15b/0x170* 
[   13.921101] * [<ffffffff811afd32>] ? do_init_module+0x27/0x1d7* 
[   13.921102] * [<ffffffff811afd6a>] do_init_module+0x5f/0x1d7* 
[   13.921104] * [<ffffffff8112c614>] load_module+0x20c4/0x26f0* 
[   13.921105] * [<ffffffff81128f50>] ? __symbol_put+0x60/0x60* 
[   13.921107] * [<ffffffff8123f474>] ? vfs_read+0x114/0x130* 
[   13.921108] * [<ffffffff8112ceb6>] SYSC_finit_module+0xe6/0x120* 
[   13.921109] * [<ffffffff8112cf0e>] SyS_finit_module+0xe/0x10* 
[   13.921111] * [<ffffffff817c7632>] entry_SYSCALL_64_fastpath+0x1a/0xa4* 
[   13.921119] Code*: 02 00 8b 75 ac 4c 89 e7 e8 94 75 00 00 85 c0 89 c1 0f 88 ae 00 00 00 49 8b 7c 24 10 e8 00 6f c2 ff 85 c0 89 c1 0f 88*
 
[   13.921123] RIP  [<ffffffffc0840a4a>] usb_audio_probe+0x2ca/0x9a0 [snd_usb_audio] 
[   13.921124] * RSP <ffff8808074d7a80>* 
[   13.921124] CR2*: 0000000000000014* 
[   13.921132] *---[ end trace 29d92678e4d33f46 ]---*

Thanks,
Shawn