CVE-2026-89736

Published: September 15, 2026Last modified: September 15, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: u_audio: Fix use-after-free on sound card disconnect g_audio_cleanup() invokes snd_card_free_when_closed() to initiate sound card teardown and immediately frees the underlying struct snd_uac_chip context. However, snd_card_free_when_closed() returns asynchronously while ALSA control elements (kctls) remain open in userspace. When userspace control applications access or close these open file descriptors, kctl callbacks attempt to dereference kctl->private_data pointing to &uac->c_prm or &uac->p_prm within the freed uac structure, resulting in a use-after-free (UAF) memory corruption. Fix this issue by deferring the destruction of struct snd_uac_chip until all references to the ALSA sound card are released. Register a custom card->private_free callback (u_audio_card_free) during g_audio_setup() that frees uac and its associated playback/capture request and ring buffers only when the sound card reference count drops to zero.

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References

• https://git.kernel.org/stable/c/4e747c864a88537e18b1ffc19a1954c9686bb8e1
• https://git.kernel.org/stable/c/79a92896e2bb9471550c56fc23d8d93592f04c27
• https://git.kernel.org/stable/c/858965947081d10d41d9a1010a540d3d5eea958b
• https://git.kernel.org/stable/c/c74ff0b1a0fca53d3ac185873c87d6a719b30a47