tls: Skip tls_append_frag on zero copy size

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>

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index 12f7b56..af875ad 100644 (file)
--- 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) {