linux-kernel - Re: TLS zerocopy sendfile offset causes data corruption

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Date:   Fri, 3 Mar 2023 17:17:56 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Adrien Moulin <amoulin@...p.free.fr>
Cc:     Boris Pismenny <borisp@...dia.com>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tariq Toukan <tariqt@...dia.com>
Subject: Re: TLS zerocopy sendfile offset causes data corruption

On Fri, 3 Mar 2023 13:07:15 +0100 (CET) Adrien Moulin wrote:
> When doing a sendfile call on a TLS_TX_ZEROCOPY_RO-enabled socket with an offset that is neither zero nor 4k-aligned, and with a "count" bigger than a single TLS record, part of the data received will be corrupted.
> 
> I am seeing this on 5.19 and 6.2.1 (x86_64) with a ConnectX-6 Dx NIC, with TLS NIC offload including sendfile otherwise working perfectly when not using TLS_TX_ZEROCOPY_RO.
> I have a simple reproducer program available here https://gist.github.com/elyosh/922e6c15f8d4d7102c8ac9508b0cdc3b

Would you be able to test potential fixes? Unfortunately testing
requires access to the right HW :(

I think the offset needs to be incremented, so:

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index 6c593788dc25..a7cc4f9faac2 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -508,6 +508,8 @@ static int tls_push_data(struct sock *sk,
 			zc_pfrag.offset = iter_offset.offset;
 			zc_pfrag.size = copy;
 			tls_append_frag(record, &zc_pfrag, copy);
+
+			iter_offset.offset += copy;
 		} else if (copy) {
 			copy = min_t(size_t, copy, pfrag->size - pfrag->offset);