net: tls: fix device-offloaded sendpage straddling records

Adrien reports that incorrect data is transmitted when a single
page straddles multiple records. We would transmit the same
data in all iterations of the loop.

Reported-by: Adrien Moulin <[email protected]>
Link: https://lore.kernel.org/all/[email protected]
Fixes: c1318b3 ("tls: Add opt-in zerocopy mode of sendfile()")
Tested-by: Adrien Moulin <[email protected]>
Reviewed-by: Tariq Toukan <[email protected]>
Acked-by: Maxim Mikityanskiy <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: kuba-moo

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);