From: Maxim Mikityanskiy <maximmi@nvidia.com>
Date: Tue, 26 Apr 2022 18:49:49 +0300
Subject: tls: Skip tls_append_frag on zero copy size
Patch-mainline: v5.18-rc5
Git-commit: a0df71948e9548de819a6f1da68f5f1742258a52
References: git-fixes

Calling tls_append_frag when max_open_record_len == record->len might
add an empty fragment to the TLS record if the call happens to be on the
page boundary. Normally tls_append_frag coalesces the zero-sized
fragment to the previous one, but not if it's on page boundary.

If a resync happens then, the mlx5 driver posts dump WQEs in
tx_post_resync_dump, and the empty fragment may become a data segment
with byte_count == 0, which will confuse the NIC and lead to a CQE
error.

This commit fixes the described issue by skipping tls_append_frag on
zero size to avoid adding empty fragments. The fix is not in the driver,
because an empty fragment is hardly the desired behavior.

Fixes: e8f69799810c ("net/tls: Add generic NIC offload infrastructure")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20220426154949.159055-1-maximmi@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/tls/tls_device.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -483,11 +483,13 @@ handle_error:
 		copy = min_t(size_t, size, (pfrag->size - pfrag->offset));
 		copy = min_t(size_t, copy, (max_open_record_len - record->len));
 
-		rc = tls_device_copy_data(page_address(pfrag->page) +
-					  pfrag->offset, copy, msg_iter);
-		if (rc)
-			goto handle_error;
-		tls_append_frag(record, pfrag, copy);
+		if (copy) {
+			rc = tls_device_copy_data(page_address(pfrag->page) +
+						  pfrag->offset, copy, msg_iter);
+			if (rc)
+				goto handle_error;
+			tls_append_frag(record, pfrag, copy);
+		}
 
 		size -= copy;
 		if (!size) {