Affected: Linux

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

nfc: llcp: Fix memleak in nfc_llcp_send_ui_frame().

syzbot reported various memory leaks related to NFC, struct nfc_llcp_sock, sk_buff, nfc_dev, etc. [0]

The leading log hinted that nfc_llcp_send_ui_frame() failed to allocate skb due to sock_error(sk) being -ENXIO.

ENXIO is set by nfc_llcp_socket_release() when struct nfc_llcp_local is destroyed by local_cleanup().

The problem is that there is no synchronisation between nfc_llcp_send_ui_frame() and local_cleanup(), and skb could be put into local->tx_queue after it was purged in local_cleanup():

CPU1 CPU2 ---- ---- nfc_llcp_send_ui_frame() local_cleanup() |- do { ' |- pdu = nfc_alloc_send_skb(..., &err) | . | |- nfc_llcp_socket_release(local, false, ENXIO); | |- skb_queue_purge(&local->tx_queue); | | ' | |- skb_queue_tail(&local->tx_queue, pdu); | ... | |- pdu = nfc_alloc_send_skb(..., &err) | ^._________________________________.'

local_cleanup() is called for struct nfc_llcp_local only after nfc_llcp_remove_local() unlinks…