CVE-2026-89736

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux6c67ed9ad9b83e453e808f9b31a931a20a25629b < c74ff0b1a0fca53d3ac185873c87d6a719b30a47affected
LinuxLinux6c67ed9ad9b83e453e808f9b31a931a20a25629b < 4e747c864a88537e18b1ffc19a1954c9686bb8e1affected
LinuxLinux6c67ed9ad9b83e453e808f9b31a931a20a25629b < 79a92896e2bb9471550c56fc23d8d93592f04c27affected
LinuxLinux6c67ed9ad9b83e453e808f9b31a931a20a25629b < 858965947081d10d41d9a1010a540d3d5eea958baffected
LinuxLinux3e016ef2e72da93a2ea7afbb45de1b481b44d761affected
LinuxLinux3256e152b645fc1e788ba44c2d8ced690113e3e6affected
LinuxLinux0eda2004f38d95ef5715d62be884cd344260535baffected
LinuxLinux33f341c1fc60e172a3515c51bdabee11e83d1ee9affected
LinuxLinuxb131989797f7287d7fdadb2bababc05a15d44750affected
LinuxLinux3bc7324e4911351e39c54a62e6ca46321cb10fafaffected
LinuxLinux43ca70753dfffd517d2af126da28690f8f615605affected
LinuxLinux4.14.312 < 4.15affected
LinuxLinux4.19.280 < 4.20affected
LinuxLinux5.4.240 < 5.5affected
LinuxLinux5.10.177 < 5.11affected
LinuxLinux5.15.105 < 5.16affected
LinuxLinux6.1.22 < 6.2affected
LinuxLinux6.2.9 < 6.3affected
LinuxLinux6.3affected
LinuxLinux0 < 6.3unaffected
LinuxLinux6.12.109 <= 6.12.*unaffected
LinuxLinux6.18.50 <= 6.18.*unaffected
LinuxLinux7.2.4 <= 7.2.*unaffected
LinuxLinux7.3-rc1 <= *unaffected

Weaknesses

References