nvmet-tcp: Fix potential UAF when ddgst mismatch

Shivam Kumar found via vulnerability testing:
When data digest is enabled on an NVMe/TCP connection and a digest
mismatch occurs on a non-final H2C_DATA PDU during an R2T-based
data transfer, the digest error handler in nvmet_tcp_try_recv_ddgst()
calls nvmet_req_uninit() — which performs percpu_ref_put() on the
submission queue — but does NOT mark the command as completed. It
does not set cqe->status, does not modify rbytes_done, and does not
clear any flag. When the subsequent fatal error triggers queue
teardown, nvmet_tcp_uninit_data_in_cmds() iterates all commands,
checks nvmet_tcp_need_data_in() for each one, and finds that the
already-uninited command still appears to need data (because
rbytes_done < transfer_len and cqe->status == 0). It therefore calls
nvmet_req_uninit() a second time on the same command — a double
percpu_ref_put against a single percpu_ref_get.

Reported-by: Shivam Kumar <kumar.shivam43666@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 164a564ba3b4e994ccbf437170e19ddac4fdc9a1..20f150d17a9625f6f5fa409d34511597de9902ea 100644 (file)
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -1321,8 +1321,10 @@ static int nvmet_tcp_try_recv_ddgst(struct nvmet_tcp_queue *queue)
                        queue->idx, cmd->req.cmd->common.command_id,
                        queue->pdu.cmd.hdr.type, le32_to_cpu(cmd->recv_ddgst),
                        le32_to_cpu(cmd->exp_ddgst));
-               if (!(cmd->flags & NVMET_TCP_F_INIT_FAILED))
+               if (!(cmd->flags & NVMET_TCP_F_INIT_FAILED)) {
+                       cmd->req.cqe->status = NVME_SC_CMD_SEQ_ERROR;
                        nvmet_req_uninit(&cmd->req);
+               }
                nvmet_tcp_free_cmd_buffers(cmd);
                ret = -EPROTO;
                goto out;