The Infineon PSOC 6 BLESS HCI driver in drivers/bluetooth/hci/hciinfineonpsoc6bless.c stored the outgoing HCI packet descriptor in a file-scope variable, static cystcblehcitxpacketinfot hcitxpkt. psoc6blesssend() cleared and populated that descriptor's packetType, dataLength and data fields before acquiring psoc6blessoperationsem, so the driver's serialising semaphore protected only the call into CyBLESoftHciSendAppPkt() and not the shared state that call reads.

The Bluetooth host does not guarantee a single HCI sender. Most transmissions are funnelled through the cooperative TX-processor work queue, but bthcicmdsend() deliberately bypasses btdev.cmdtxqueue for BTHCIOPHOSTNUMCOMPLETEDPACKETS and calls btsend() directly from the caller's thread; that caller is bthcihostnumcompletedpackets(), the aclinpool destroy callback, which runs on whichever thread drops the last reference to a received ACL buffer. CONFIGBTHCIACLFLOWCONTROL defaults to y on this driver's boards, and an application that returns -EINPROGRESS from its L2CAP recv callback and later calls btl2capchanrecvcomplete() performs that unref from its own preemptible thread. A remote peer that generates Bluetooth traffic concurrently with the device's own transmissions raises the collision rate.

When two senders interleave, the semaphore holder can hand the controller a descriptor whose dataLength comes from one netbuf and whose data pointer comes from another — or one whose buffer has already been returned to its pool. The controller then copies and transmits up to a full HCI/ACL payload starting at a shorter or recycled buffer, disclosing adjacent RAM contents to the connected peer; other interleavings duplicate one HCI packet and silently drop another, disrupting the link. The driver only reads through the shared descriptor, so no memory corruption or write primitive results, and the disclosed bytes are not attacker-chosen. The fix makes the descriptor a local variable in psoc6blesssend(), removing the shared state; CyBLESoftHciSendAppPkt() copies the packet before returning, so it need not outlive the call.