ncsi_send_cmd_nl() takes the number of bytes to copy from the attacker-controlled ncsi_pkt_hdr.length field of the in-band packet header, while the source buffer is the NCSI_ATTR_DATA netlink attribute whose readable size is nla_len() - sizeof(ncsi_pkt_hdr). The two length sources are never cross-checked: only nla_len() >= sizeof(struct ncsi_pkt_hdr) is enforced. With hdr->length set larger than the attribute payload (up to 65535 against at most 2032 readable bytes), ncsi_cmd_handler_oem() copies past the end of the netlink attribute buffer with unsafe_memcpy(), leaking up to ~64KB of kernel heap memory into the transmitted NCSI command packet. The destination skb is sized by the declared payload, so the write side does not overflow - this is a pure OOB read / information leak, reachable with CAP_NET_ADMIN on systems with a registered NCSI device (e.g. OpenBMC on Aspeed BMC SoCs, where NET_NCSI=y is standard). Reject commands whose declared payload extends past the end of the data attribute. The issue was found by the autokbug dynamic kernel fuzzer at Tencent Yunding Lab. Fixes: 9771b8ccdfa6 ("net/ncsi: Extend NC-SI Netlink interface to allow user space to send NC-SI command") Reported-by: Henry Martin Signed-off-by: Henry Martin --- net/ncsi/ncsi-netlink.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ncsi/ncsi-netlink.c b/net/ncsi/ncsi-netlink.c index 2f872d064396d..29f9dd0b62dc2 100644 --- a/net/ncsi/ncsi-netlink.c +++ b/net/ncsi/ncsi-netlink.c @@ -461,6 +461,11 @@ static int ncsi_send_cmd_nl(struct sk_buff *msg, struct genl_info *info) nca.req_flags = NCSI_REQ_FLAG_NETLINK_DRIVEN; nca.info = info; nca.payload = ntohs(hdr->length); + if (nca.payload > len - sizeof(*hdr)) { + /* The payload cannot extend past the data attribute */ + ret = -EINVAL; + goto out_netlink; + } nca.data = data + sizeof(*hdr); ret = ncsi_xmit_cmd(&nca); -- 2.43.0