From 14cc5a7e77731497d5bea70f3bb05df7eda982e4 Mon Sep 17 00:00:00 2001 From: Shivam Kumar Date: Fri, 14 Aug 2026 15:48:11 -0400 Subject: [PATCH] nvmet-tcp: fix out-of-bounds write when receiving an over-long PDU nvmet_tcp_try_recv_pdu() reads a PDU header into the fixed 128-byte queue->pdu union, then computes the remaining payload length as queue->left = hdr->hlen - queue->offset + hdgst; and reads that many more bytes into &queue->pdu + queue->offset, without ever bounding the result against sizeof(queue->pdu). A struct nvme_tcp_icreq_pdu is itself 128 bytes, exactly the size of the union. Once a header digest has been negotiated (hdgst = 4), a second ICReq passes the hlen == nvmet_tcp_pdu_size() check but yields queue->left = 128 - 8 + 4 = 124, so bytes 8..132 are written into the 128-byte buffer -- 4 bytes past its end, over queue->hdr_digest and queue->data_digest. Those bytes are attacker-controlled (an ICReq carries no digest), and the duplicate ICReq is only rejected later, after the overflow. A remote unauthenticated host can thus corrupt kernel memory adjacent to the receive buffer. Reject any PDU whose declared length would read past the end of queue->pdu before the second recv. Fixes: 872d26a391da ("nvmet-tcp: add NVMe over TCP target driver") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Shivam Kumar Cc: stable@vger.kernel.org Reviewed-by: Sagi Grimberg Signed-off-by: Keith Busch --- drivers/nvme/target/tcp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c index e4f603b2ace7..1e2346ede900 100644 --- a/drivers/nvme/target/tcp.c +++ b/drivers/nvme/target/tcp.c @@ -1244,6 +1244,8 @@ static int nvmet_tcp_try_recv_pdu(struct nvmet_tcp_queue *queue) } queue->left = hdr->hlen - queue->offset + hdgst; + if (queue->left > sizeof(queue->pdu) - queue->offset) + return -EPROTO; goto recv; }