CVE-2025-37918

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

Bluetooth: btusb: avoid NULL pointer dereference in skb_dequeue()

A NULL pointer dereference can occur in skb_dequeue() when processing a QCA firmware crash dump on WCN7851 (0489:e0f3).

[ 93.672166] Bluetooth: hci0: ACL memdump size(589824)

[ 93.672475] BUG: kernel NULL pointer dereference, address: 0000000000000008 [ 93.672517] Workqueue: hci0 hci_devcd_rx [bluetooth] [ 93.672598] RIP: 0010:skb_dequeue+0x50/0x80

The issue stems from handle_dump_pkt_qca() returning 0 even when a dump packet is successfully processed. This is because it incorrectly forwards the return value of hci_devcd_init() (which returns 0 on success). As a result, the caller (btusb_recv_acl_qca() or btusb_recv_evt_qca()) assumes the packet was not handled and passes it to hci_recv_frame(), leading to premature kfree() of the skb.

Later, hci_devcd_rx() attempts to dequeue the same skb from the dump queue, resulting in a NULL pointer dereference.

Fix this by:

1. Making handle_dump_pkt_qca() return 0 on success and negative errno on failure, consistent with kernel conventions.
2. Splitting dump packet detection into separate functions for ACL and event packets for better structure and readability.

This ensures dump packets are properly identified and consumed, avoiding double handling and preventing NULL pointer access.

A vulnerability was discovered in the btusb driver when processing QCA crash dump packets on WCN7851 chipsets. An incorrect return value caused certain packets to be handled twice, resulting in a NULL pointer dereference in skb_dequeue(). Local attackers with low privileges could trigger this condition to cause a kernel crash, leading to denial of service (DoS).

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.