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nfc: llcp: reject PDUs shorter than the LLCP header
In the Linux kernel, the following vulnerability has been resolved: nfc: llcp: reject PDUs shorter than the LLCP header Every LLCP PDU begins with a two-byte header (DSAP/SSAP + PTYPE), but the receive path never checked that a frame is at least LLCP_HEADER_SIZE bytes before parsing it. nfc_llcp_rx_skb() reads the header via nfc_llcp_ptype()/nfc_llcp_dsap()/ nfc_llcp_ssap(), which dereference pdu->data[0] and pdu->data[1], and a CONNECT or CC PDU then computes tlv_array_len = skb->len - LLCP_HEADER_SIZE; as a size_t and hands it to the TLV walk. When the frame is shorter than the header the subtraction wraps to a huge value and the walk runs far past the buffer, an out-of-bounds read. A nearby NFC device can reach this without authentication; LLCP link activation happens automatically after NFC-DEP. Guard the common receive choke point __nfc_llcp_recv(), shared by both the target (nfc_llcp_data_received()) and initiator (nfc_llcp_recv()) paths, so a short skb is dropped before the rx_work worker parses it. Use pskb_may_pull() rather than a skb->len test so the two header bytes are guaranteed to sit in the skb linear area even for a non-linear skb, matching how the sibling NCI and HCI receive paths validate their headers. Reproduced with a KFENCE out-of-bounds read via /dev/virtual_nci on linux-next. Found by 0sec automated security-research tooling (https://0sec.ai).
References
Affected products
- <e6ec76a68dce04884dfeccfe5a5f0e9f67c0ec82
- <eab47618e282602197db287ecbd1b09d356a2515
- =<7.1.*
- ==3.3
- <a7b9b449f5a5132221fff6adc11a9431ab8cd914
- =<6.18.*
- <f36cffea24bf3e2cc29a00d4b51dbcadc087d810
- =<6.12.*
- =<7.2.*
- <ae5f20f5842f440b72d030e3a34fe182dd8eae42
- =<5.10.*
- =<5.15.*
- <95674f506c6376d6722a23144c9acd26609771ed
- =<6.6.*
- <e969e98410051b1ef8cc318bfe0c7e3f24ec766d
- <d3d90243393c48146911c67fd3792b549d21d9e6
- <3793d768b40f38bb97265dd5b9a8b8655c4e1b1d
- =<*
- =<6.1.*
- <3.3