[PATCH 5.10 43/77] nvme-tcp: fix possible req->offset corruption

Greg Kroah-Hartman
2021-11-01T09:35:36Z

From: Varun Prakash <varun@chelsio.com>

commit ce7723e9cdae4eb3030da082876580f4b2dc0861 upstream.

With commit db5ad6b7f8cd ("nvme-tcp: try to send request in queue_rq
context") r2t and response PDU can get processed while send function
is executing.

Current data digest send code uses req->offset after kernel_sendmsg(),
this creates a race condition where req->offset gets reset before it
is used in send function.

This can happen in two cases -
1. Target sends r2t PDU which resets req->offset.
2. Target send response PDU which completes the req and then req is
used for a new command, nvme_tcp_setup_cmd_pdu() resets req->offset.

Fix this by storing req->offset in a local variable and using
this local variable after kernel_sendmsg().

Fixes: db5ad6b7f8cd ("nvme-tcp: try to send request in queue_rq context")
Signed-off-by: Varun Prakash <varun@chelsio.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/nvme/host/tcp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1037,6 +1037,7 @@ static int nvme_tcp_try_send_data_pdu(st
static int nvme_tcp_try_send_ddgst(struct nvme_tcp_request *req)
{
struct nvme_tcp_queue *queue = req->queue;
+ size_t offset = req->offset;
int ret;
struct msghdr msg = { .msg_flags = MSG_DONTWAIT };
struct kvec iov = {
@@ -1053,7 +1054,7 @@ static int nvme_tcp_try_send_ddgst(struc
if (unlikely(ret <= 0))
return ret;

- if (req->offset + ret == NVME_TCP_DIGEST_LENGTH) {
+ if (offset + ret == NVME_TCP_DIGEST_LENGTH) {
nvme_tcp_done_send_req(queue);
return 1;
}