CVE-2026-74509: Bluetooth: hci_sync: Fix advertising data UAFs

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

Bluetooth: hcisync: Fix advertising data UAFs

hcifindadvinstance() returns an advinfo pointer that is valid only while hdev->lock is held. The advertising command-sync paths perform instance lookups without that lock and, in some cases, retain the pointer while waiting for a controller response.

An advertising termination event can therefore interleave as follows:

hcicmdsyncwork hcirxwork hcifindadvinstance() hcicmdsyncstatus() wait for controller reply hcidevlock() hciremoveadvinstance() kfree(adv) adv->scanrspchanged = false

KASAN reported:

BUG: KASAN: slab-use-after-free in hcisetextscanrspdatasync+0x2e1/0x300 Write of size 1 at addr ffff88810a45d21d by task kworker/u17:0/88 Workqueue: hci0 hcicmdsyncwork Call Trace: hcisetextscanrspdatasync+0x2e1/0x300 hcischeduleadvinstancesync+0x390/0x4c0 hcicmdsyncwork+0x173/0x300 Allocated by task 87: hciaddadvinstance+0x538/0xac0 addadvertising+0x885/0x1160 Freed by task 89: kfree+0x131/0x3c0 hciremoveadvinstance+0x1d8/0x3b0 hcileextadvtermevt+0x17b/0x730

Protect the instance lookup and payload construction in the extended advertising, scan response, and periodic advertising data paths. Snapshot the advertising parameters under hdev->lock, but release the lock before waiting for the controller.

Clear advertising-data dirty bits before issuing their commands and restore them after a failure using a fresh lookup. Likewise, update the reported transmit power through a fresh lookup after the parameter command completes. No advinfo pointer then survives an HCI command wait.