Bluetooth: hci_conn: fix potential UAF in create_big_sync

Overview

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

Bluetooth: hci_conn: fix potential UAF in create_big_sync

Add hci_conn_valid() check in create_big_sync() to detect stale connections before proceeding with BIG creation. Handle the resulting -ECANCELED in create_big_complete() and re-validate the connection under hci_dev_lock() before dereferencing, matching the pattern used by create_le_conn_complete() and create_pa_complete().

Keep the hci_conn object alive across the async boundary by taking a reference via hci_conn_get() when queueing create_big_sync(), and dropping it in the completion callback. The refcount and the lock are complementary: the refcount keeps the object allocated, while hci_dev_lock() serializes hci_conn_hash_del()'s list_del_rcu() on hdev->conn_hash, as required by hci_conn_del().

hci_conn_put() is called outside hci_dev_unlock() so the final put (which resolves to kfree() via bt_link_release) does not run under hdev->lock, though the release path would be safe either way.

Without this, create_big_complete() would unconditionally dereference the conn pointer on error, causing a use-after-free via hci_connect_cfm() and hci_conn_del().

Affected

• Linux >= eca0ae4aea66914515e5e3098ea051b518ee5316 < d41093723e47255d7d74df86e2736711c1b8486e
• Linux >= eca0ae4aea66914515e5e3098ea051b518ee5316 < 6823f730bf195fc296d9edd09e2ca94bc1ff5584
• Linux >= eca0ae4aea66914515e5e3098ea051b518ee5316 < 1750a2df0eab61dc421a7afae74abdd239a44b85
• Linux >= eca0ae4aea66914515e5e3098ea051b518ee5316 < dc34f8d8240f25dd137dc2758ebbcc75e3779142
• Linux >= eca0ae4aea66914515e5e3098ea051b518ee5316 < f8eaf92c57ad99358dd372580d5ff87623343a72
• Linux >= eca0ae4aea66914515e5e3098ea051b518ee5316 < 0beddb0c380bed5f5b8e61ddbe14635bb73d0b41
• Linux 6.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.