CVE-2026-80971 in Linux
الملخص
بحسب MITRE • 11/09/2026
In the Linux kernel, the following vulnerability has been resolved:
ALSA: bcd2000: clear the URB pointers on disconnect
bcd2000_free_usb_related_resources() frees both URBs and leaves the pointers behind:
usb_kill_urb(bcd2k->midi_out_urb); usb_kill_urb(bcd2k->midi_in_urb);
usb_free_urb(bcd2k->midi_out_urb); usb_free_urb(bcd2k->midi_in_urb);
The rawmidi device outlives that call. A substream that is still open when the device is unplugged reaches bcd2000_midi_send() from the trigger path on close. That function writes to the freed URB and then hands it to the USB core:
bcd2k->midi_out_urb->transfer_buffer_length = BUFSIZE; ... ret = usb_submit_urb(bcd2k->midi_out_urb, GFP_ATOMIC);
usb_kill_urb() does not stop a later submission either, so a submit that races the disconnect can requeue the URB after it has been reaped. midi_in_urb is exposed the same way: bcd2000_input_complete() resubmits it from the completion handler.
KASAN on 7.2.0-rc5 (arm64):
BUG: KASAN: slab-use-after-free in bcd2000_midi_send [snd_bcd2000]
Write of size 4 at addr ffff00001827d388 by task bpoc/168 __asan_store4 bcd2000_midi_send [snd_bcd2000]
bcd2000_midi_output_trigger [snd_bcd2000]
snd_rawmidi_kernel_write1 close_substream.part.0 Freed by task 168: usb_free_urb bcd2000_disconnect [snd_bcd2000]
BUG: KASAN: slab-use-after-free in usb_submit_urb Read of size 8 at addr ffff00001827d3b8 by task bpoc/168
Clear both pointers after freeing and test them on the paths that can still run. Poison the URBs before freeing them: usb_poison_urb() waits for a running completion handler and rejects any later submission, so after it returns the input path is quiesced and only the rawmidi trigger path can still reach bcd2000_midi_send(). No unpoison is needed; the URBs are freed on the next line.
Discovered by XBOW, triaged by Baul Lee <[email protected]>
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