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    Subject[PATCH 5.17 145/225] tls: Skip tls_append_frag on zero copy size
    Date
    From: Maxim Mikityanskiy <maximmi@nvidia.com>

    [ Upstream commit a0df71948e9548de819a6f1da68f5f1742258a52 ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/tls/tls_device.c | 12 +++++++-----
    1 file changed, 7 insertions(+), 5 deletions(-)

    diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
    index b932469ee69c..a40553e83f8b 100644
    --- a/net/tls/tls_device.c
    +++ b/net/tls/tls_device.c
    @@ -483,11 +483,13 @@ static int tls_push_data(struct sock *sk,
    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) {
    --
    2.35.1


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