CVE-2026-98735

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

Bluetooth: hci_core: Serialize ACL scheduling with channel deletion

hci_chan_sent() selects a channel under RCU but drops the read lock before accessing chan->conn and returning the channel. The ACL and LE schedulers then use its packet queue and update its transmit counters without any protection against channel deletion.

After TX selects a channel and releases RCU, a disconnect command timeout on the separate request workqueue can run hci_conn_failed() and l2cap_conn_del(). hci_chan_del() can then unlink the channel, complete synchronize_rcu(), purge its queue and free it before TX resumes. This causes use-after-free both in hci_chan_sent() and in its callers.

KASAN reported:

BUG: KASAN: slab-use-after-free in hci_chan_sent+0x892/0x9b0 Workqueue: hci0 hci_tx_work Call Trace: hci_chan_sent+0x892/0x9b0 hci_tx_work+0x5e6/0xb70 Allocated by task 91: hci_chan_create+0xe3/0x350 l2cap_conn_add.part.0+0x12/0xa30 l2cap_chan_connect+0x110d/0x1b60 l2cap_sock_connect+0x310/0x530 Freed by task 99: hci_chan_del+0x11f/0x170 l2cap_conn_del+0x4f1/0x800 l2cap_connect_cfm+0x88c/0xd30 hci_conn_failed+0x150/0x250 hci_abort_conn_sync+0x3e3/0x800 hci_cmd_sync_run+0x7e/0xc0 hci_abort_conn+0x105/0x1f0 disconnect_sync+0x157/0x290 hci_cmd_sync_work+0x13c/0x290

Hold the existing device mutex across channel selection and transmission in both schedulers to serialize them with channel teardown. Keep timeout handling outside the critical sections because hci_link_tx_to() acquires the same mutex. This also permits the transmit path to sleep, unlike extending the RCU read-side critical section across packet submission.

Affected Software

References

• https://git.kernel.org/stable/c/126714c495bf31a5e71411b8e0b65a685bb5e58d
• https://git.kernel.org/stable/c/4fda8f0abeea9929036446d89a476fb8298abcb0
• https://git.kernel.org/stable/c/51f95ea451f25d7e3f048c0f438f04fa74688aae
• https://git.kernel.org/stable/c/74667f6eb7c12b65c56e02e0f527e4099db4ebfd
• https://git.kernel.org/stable/c/780affacd92977fd9b819bdc4f26a6832cb27fda
• https://git.kernel.org/stable/c/7fbeda3dcd5f54e7429f4b5e2cfa7344b7e9b1c9
• https://git.kernel.org/stable/c/86e9708f9d19a7f1bd5dc9c1652d07707f79f5bd
• https://git.kernel.org/stable/c/f4845ab191a4f686a5da481fbba90ed73bb693b0