Re: [PATCH v4] nvme-tcp: fix connect failure on receiving partial ICResp PDU

[Hannes Reinecke]

On 1/27/25 08:37, Hannes Reinecke wrote:
> On 1/24/25 19:43, Caleb Sander Mateos wrote:
> > nvme_tcp_init_connection() attempts to receive an ICResp PDU but only
> > checks that the return value from recvmsg() is non-negative. If the
> > sender closes the TCP connection or sends fewer than 128 bytes, this
> > check will pass even though the full PDU wasn't received.
> >
> > Ensure the full ICResp PDU is received by checking that recvmsg()
> > returns the expected 128 bytes.
> >
> > Additionally set the MSG_WAITALL flag for recvmsg(), as a sender could
> > split the ICResp over multiple TCP frames. Without MSG_WAITALL,
> > recvmsg() could return prematurely with only part of the PDU.
> >
> > Signed-off-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
> > Fixes: 3f2304f8c6d6 ("nvme-tcp: add NVMe over TCP host driver")
> > ---
> > v4: keep recvmsg() error return value
> > v3: fix return value to indicate error
> > v2: add Fixes tag
> >
> >   drivers/nvme/host/tcp.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> > index e9ff6babc540..56679eb8c0d6 100644
> > --- a/drivers/nvme/host/tcp.c
> > +++ b/drivers/nvme/host/tcp.c
> > @@ -1446,15 +1446,18 @@ static int nvme_tcp_init_connection(struct 
> > nvme_tcp_queue *queue)
> >       iov.iov_len = sizeof(*icresp);
> >       if (nvme_tcp_queue_tls(queue)) {
> >           msg.msg_control = cbuf;
> >           msg.msg_controllen = sizeof(cbuf);
> >       }
> > +    msg.msg_flags = MSG_WAITALL;
> >       ret = kernel_recvmsg(queue->sock, &msg, &iov, 1,
> >               iov.iov_len, msg.msg_flags);
>
> But won't we have to wait for a TCP timeout now if the sender sends less 
> than 128 bytes? With this patch we always wait for 128 bytes, and
> possibly wait for TCP timeout if not.
> Testcase for this would be nice ...
>
> And I need to check if secure concatenation is affected here; with
> secure concatenation we need to peek at the first packet to check
> if it's an ICRESP or a TLS negotiation.
And wouldn't this patch be sufficient here?

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 841238f38fdd..85b1328a8757 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1451,12 +1451,13 @@ static int nvme_tcp_init_connection(struct 
nvme_tcp_queue *queue)
        }
        ret = kernel_recvmsg(queue->sock, &msg, &iov, 1,
                        iov.iov_len, msg.msg_flags);
+       if (ret == 0)
+               ret = -ENOTCONN;
        if (ret < 0) {
                pr_warn("queue %d: failed to receive icresp, error %d\n",
                        nvme_tcp_queue_id(queue), ret);
                goto free_icresp;
        }
-       ret = -ENOTCONN;
        if (nvme_tcp_queue_tls(queue)) {
                ctype = tls_get_record_type(queue->sock->sk,
                                            (struct cmsghdr *)cbuf);

icresp validity is checked later in the code, so if we haven't received
a full icresp we _should_ fail those tests. And then we don't really
have to check how many bytes we've received.

Cheers,

Hannes
--
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@xxxxxxx                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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