llc_shdlc_deinit() purges SHDLC skb queues and frees the llc_shdlc structure while its timers and state machine work may still be active. Timer callbacks can schedule sm_work, and sm_work accesses SHDLC state and the skb queues. If teardown happens in parallel with a queued/running work item, it can lead to UAF and other shutdown races. Stop all SHDLC timers and cancel sm_work synchronously before purging the queues and freeing the context. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: 4a61cd6687fc ("NFC: Add an shdlc llc module to llc core") Signed-off-by: Votokina Victoria --- net/nfc/hci/llc_shdlc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/nfc/hci/llc_shdlc.c b/net/nfc/hci/llc_shdlc.c index 4fc37894860c..08c8aa1530d8 100644 --- a/net/nfc/hci/llc_shdlc.c +++ b/net/nfc/hci/llc_shdlc.c @@ -762,6 +762,14 @@ static void llc_shdlc_deinit(struct nfc_llc *llc) { struct llc_shdlc *shdlc = nfc_llc_get_data(llc); + timer_shutdown_sync(&shdlc->connect_timer); + timer_shutdown_sync(&shdlc->t1_timer); + timer_shutdown_sync(&shdlc->t2_timer); + shdlc->t1_active = false; + shdlc->t2_active = false; + + cancel_work_sync(&shdlc->sm_work); + skb_queue_purge(&shdlc->rcv_q); skb_queue_purge(&shdlc->send_q); skb_queue_purge(&shdlc->ack_pending_q); -- 2.43.0