[PATCH v2 5.15.y] nvmet-tcp: Fix potential UAF when ddgst mismatch

[Shivam Kumar <kumar.shivam43666@gmail.com>]

commit dbbd07d0a7020b80f6a7028e561908f7b83b3d5a upstream.

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>
Signed-off-by: Shivam Kumar <kumar.shivam43666@gmail.com>
---
 drivers/nvme/target/tcp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index a8ff08c81..48e46eb3c 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -1212,8 +1212,10 @@ 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);
 		nvmet_tcp_fatal_error(queue);
 		ret = -EPROTO;
-- 
2.50.1 (Apple Git-155)