In the Linux kernel, the following vulnerability has been resolved: nfc: llcp: bound SNL TLV parsing to the skb and add length checks nfc_

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

nfc: llcp: bound SNL TLV parsing to the skb and add length checks

nfc_llcp_recv_snl() walked the SNL TLV list using a u16 offset/length
pair derived from skb->len, without bounding reads to the actual skb
data. Three problems followed:

• For a short frame (skb->len < LLCP_HEADER_SIZE), tlv_len underflowed.
• The per-TLV header (type, length) was read without checking that two
  bytes remained.
• A declared TLV length could run past the end of the buffer, and an
  SDREQ with length == 0 made "service_name_len = length - 1" underflow
  (size_t), driving an out-of-bounds read in the following strncmp() /
  nfc_llcp_sock_from_sn(). The SDRES case likewise read tlv[2]/tlv[3]
  without a length check.

A nearby NFC device can reach this without authentication; LLCP link
activation happens automatically after NFC-DEP.

Walk the TLV list by pointer, bounded by skb_tail_pointer() over the
linear skb data, and validate each TLV declared length before use. Add
explicit length checks for SDREQ (>= 1) and SDRES (exactly 2).

Found by 0sec automated security-research tooling (https://0sec.ai).