[PATCH 5.15 116/177] tls: Skip tls_append_frag on zero copy size

Greg Kroah-Hartman
2022-05-04T17:42:22Z

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