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Commitdbf666e4fc("Bluetooth: HIDP: Fix possible UAF") made hidp_session_remove() drop the L2CAP reference and set session->conn = NULL once the session is considered removed, and added a bare if (session->conn) guard around the kthread-exit l2cap_unregister_user() call in hidp_session_thread(). The sibling ioctl site in hidp_connection_del() still reads session->conn unlocked and unguarded, and the kthread-exit guard itself is a lockless double-read. hidp_session_find() drops hidp_session_sem before returning, so hidp_session_remove() can null session->conn between the lookup and the call in hidp_connection_del(). Worse, since commit752a6c9596("Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user") takes mutex_lock(&conn->lock) inside l2cap_unregister_user(), a stale non-NULL snapshot also UAFs on conn->lock. v1 only added an if (session->conn) guard at the ioctl site, which doesn't address either race; Luiz suggested snapshotting session->conn under the sem and clearing it before the call. Taking hidp_session_sem across l2cap_unregister_user() would be wrong: l2cap_conn_del() already establishes the lock order conn->lock -> hidp_session_sem via l2cap_unregister_all_users() -> user->remove == hidp_session_remove(), so taking hidp_session_sem before conn->lock would AB/BA deadlock. Factor a helper hidp_session_unregister_conn() that under down_write(&hidp_session_sem) snapshots session->conn and clears the member, then outside the sem calls l2cap_unregister_user() and l2cap_conn_put() on the snapshot. Call it from both hidp_connection_del() and hidp_session_thread()'s exit path. At most one consumer wins the write-sem; later callers observe session->conn == NULL and skip the unregister and put, so the reference hidp_session_new() took via l2cap_conn_get() is consumed exactly once. session_free() already tolerates a NULL session->conn. Fixes:dbf666e4fc("Bluetooth: HIDP: Fix possible UAF") Suggested-by: Luiz Augusto von Dentz <luiz.dentz@gmail.com> Link: https://lore.kernel.org/all/20260422011437.176643-1-michael.bommarito@gmail.com/ Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com> Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
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