CVE-2026-68189: Bluetooth: hci_sync: Protect UUID list traversal

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

Bluetooth: hcisync: Protect UUID list traversal

The hcisync conversion moved class-of-device and EIR generation from an HCI request built under hdev->lock to asynchronous command sync work. The worker holds hdev->reqlock, but that lock does not serialize access to hdev->uuids against adduuid() and removeuuid(), which update the list under hdev->lock.

The following interleaving can therefore occur:

CPU0 (command sync work) CPU1 (management socket) fetch uuid from the list listdel(&uuid->list) kfree(uuid) read uuid->size

KASAN reports the resulting use-after-free:

BUG: KASAN: slab-use-after-free in eircreate+0xb8f/0xee0 Read of size 1 at addr ffff88810dbd8620 by task kworker/u17:0/87 Workqueue: hci0 hcicmdsyncwork Call Trace: eircreate+0xb8f/0xee0 hciupdateeirsync+0x1c0/0x330 hcicmdsyncwork+0x13c/0x290 processonework+0x63a/0x1070 workerthread+0x45b/0xd10

Allocated by task 86: kasankmalloc+0x8f/0xa0 adduuid+0x18a/0x4b0 hcisocksendmsg+0x1033/0x1ea0

Freed by task 92: kasanslabfree+0x43/0x70 kfree+0x131/0x3c0 removeuuid+0x25e/0x560 hcisocksendmsg+0x1033/0x1ea0

Hold hdev->lock while generating and committing the class-of-device and EIR snapshots. Release it before sending an HCI command, so controller waits do not happen under the device lock. This protects all UUID list walks in these paths and restores the serialization lost in the command sync conversion.