nvme-tcp: fix NULL pointer dereferences in nvmet_tcp_build_pdu_iovec

shivam-2315 · gregkh · commit fdecd3b6aac1 · 2026-01-30T10:27:23.000+01:00
[ Upstream commit 32b63ac ] Commit efa5630 ("nvmet-tcp: Fix a kernel panic when host sends an invalid H2C PDU length") added ttag bounds checking and data_offset validation in nvmet_tcp_handle_h2c_data_pdu(), but it did not validate whether the command's data structures (cmd->req.sg and cmd->iov) have been properly initialized before processing H2C_DATA PDUs. The nvmet_tcp_build_pdu_iovec() function dereferences these pointers without NULL checks. This can be triggered by sending H2C_DATA PDU immediately after the ICREQ/ICRESP handshake, before sending a CONNECT command or NVMe write command. Attack vectors that trigger NULL pointer dereferences: 1. H2C_DATA PDU sent before CONNECT → both pointers NULL 2. H2C_DATA PDU for READ command → cmd->req.sg allocated, cmd->iov NULL 3. H2C_DATA PDU for uninitialized command slot → both pointers NULL The fix validates both cmd->req.sg and cmd->iov before calling nvmet_tcp_build_pdu_iovec(). Both checks are required because: - Uninitialized commands: both NULL - READ commands: cmd->req.sg allocated, cmd->iov NULL - WRITE commands: both allocated Fixes: efa5630 ("nvmet-tcp: Fix a kernel panic when host sends an invalid H2C PDU length") Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: Shivam Kumar <kumar.shivam43666@gmail.com> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
@@ -995,6 +995,18 @@ static int nvmet_tcp_handle_h2c_data_pdu(struct nvmet_tcp_queue *queue)
 		pr_err("H2CData PDU len %u is invalid\n", cmd->pdu_len);
 		goto err_proto;
 	}
+       /*
+	* Ensure command data structures are initialized. We must check both
+	* cmd->req.sg and cmd->iov because they can have different NULL states:
+	* - Uninitialized commands: both NULL
+	* - READ commands: cmd->req.sg allocated, cmd->iov NULL
+	* - WRITE commands: both allocated
+	*/
+	if (unlikely(!cmd->req.sg || !cmd->iov)) {
+		pr_err("queue %d: H2CData PDU received for invalid command state (ttag %u)\n",
+			queue->idx, data->ttag);
+		goto err_proto;
+	}
 	cmd->pdu_recv = 0;
 	nvmet_tcp_build_pdu_iovec(cmd);
 	queue->cmd = cmd;
