CVE-2026-98736

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

Bluetooth: hci conn: Lock parent access during enhanced SCO setup

Bluetooth: hci conn: Lock parent access during enhanced SCO setup

hci enhanced setup sync() runs on the request workqueue without the hci dev lock held by its caller when setup was queued. Its CVSD capability check and find next esco param() dereference conn->parent while the receive workqueue can unlink and release that parent.

The following interleaving can cause a use-after-free:

hci enhanced setup sync() hci disconn complete evt() load conn->parent hci dev lock() hci conn del(ACL parent) unlink SCO child drop link's parent reference clear child->parent release ACL parent bt link release() kfree(parent) hci dev unlock() read parent->features[0][3]

The reference held for the queued SCO child does not keep its ACL parent alive after unlinking. Commit 42de40abe25d ("Bluetooth: hci conn: fix the SCO setup context lifetime") protects the child stored in the queued context, but leaves these parent accesses unprotected.

With a 40 ms diagnostic delay after loading conn->parent, an instrumented kernel based on fd179f8a05be, which already contains 42de40abe25d,

BUG: KASAN: slab-use-after-free in hci enhanced setup sync+0xda5/0xdf0 Read of size 1 at addr ffff888102204047 by task kworker/u17:0/93 Call Trace: hci enhanced setup sync+0xda5/0xdf0 hci cmd sync work+0x13c/0x290 process one work+0x6b4/0x10e0

Allocated by task 92: hci conn add+0x304/0x1df0 hci connect acl+0x349/0x3e0 hci connect sco+0x3b/0x9a0 sco sock connect+0x475/0xca0

Freed by task 94: kfree+0x121/0x3c0 bt link release+0x79/0xa0 device release+0xc8/0x240 kobject put+0x14d/0x280 hci conn del+0x524/0xe30 hci disconn complete evt+0x403/0x8c0 hci event packet+0x71b/0xb20 hci rx work+0x293/0x730

The accessed address is 71 bytes into the freed ACL parent, at its features[0][3] byte; the queued SCO child is a different object. The diagnostic preserves the loaded parent across the delay, matching the unmodified compiled capability check, and does not change the parent references or teardown path.

Hold hci dev lock() across the codec switch, including every call to find next esco param(), and release it on all selection errors. Keep configure datapath sync() outside the critical section because it waits for HCI events. Preserve parameter selection and existing return values.