CVE-2026-98836

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

ALSA: line6: reject oversized playback packets

Each playback URB is handed a slice of out.buffer that is exactly LINE6_ISO_PACKETS * max_packet_size_out bytes, sized from the OUT endpoint, but the number of bytes written into that slice is never compared against it.

submit_audio_out_urb() takes the frame count from prev_fsize, which audio_in_callback() derived from the IN endpoints received packet length, and rescales it with the playback frame size; when prev_fsize is still zero it synthesizes a length from the sample rate instead. On a device declaring a large IN wMaxPacketSize and a small OUT wMaxPacketSize, the resulting memcpy(), or the memset() when the playback stream is idle, runs past its slice and, as the reproducer below shows, beyond the allocation.

usb_submit_urb() is not a backstop. max_packet_size_out comes from usb_maxpacket(), which returns only the low 11 bits of wMaxPacketSize, while USB core validates a high-speed isochronous length against that base scaled by usb_endpoint_maxp_mult(). A length of up to three times the allocated slice is therefore accepted, and even a rejected URB is only rejected after the write.

Reject a packet that does not fit the slice the driver allocated for it. Clamping it instead would silently shorten the capture-derived rate feedback and desynchronize the two streams.

BUG: KASAN: slab-out-of-bounds in submit_audio_out_urb (sound/usb/line6/playback.c:229) Write of size 1024 at addr ffff888100bbd400 by task kworker/1:2/5002 Workqueue: events line6_startup_work Call Trace: __asan_memcpy (mm/kasan/shadow.c:106) submit_audio_out_urb (sound/usb/line6/playback.c:229) line6_submit_audio_out_all_urbs (sound/usb/line6/playback.c:291) line6_stream_start (sound/usb/line6/pcm.c:194) line6_pcm_acquire (sound/usb/line6/pcm.c:337) line6_startup_work (sound/usb/line6/driver.c:728) process_one_work (kernel/workqueue.c:3396) worker_thread (kernel/workqueue.c:3479 kernel/workqueue.c:3560) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245)

The buggy address belongs to the object at ffff888100bbd400 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 0 bytes inside of allocated 256-byte region [ffff888100bbd400, ffff888100bbd500)

Affected Software

References

• https://git.kernel.org/stable/c/3f75da1e4ee699f6650d23d6897cf443b01856c7
• https://git.kernel.org/stable/c/48c76820dd8858ce60a6e42519141ebcf3dfeebf
• https://git.kernel.org/stable/c/61b0a5a114fa4552892da5c0ff2f42e63bf08c6b
• https://git.kernel.org/stable/c/7f31587e26e1d4735924bc324e7fa506d85de150
• https://git.kernel.org/stable/c/933d8ac23388eb208ea195231d682dce0bec86ca
• https://git.kernel.org/stable/c/a84371be89c39ccc46c7af8b9eb15c448df9265f
• https://git.kernel.org/stable/c/b78748424f29f07d310484b2b36afdececa74389
• https://git.kernel.org/stable/c/e3b68b1d92f279e203923dc8bf45c8860e5b5985