net: tls: fix silent data drop under pipe back-pressure

tls_sw_splice_read() uses len when advancing rxm->offset / rxm->full_len
after skb_splice_bits(), rather than copied (the actual number of bytes
successfully spliced into the pipe). When the destination pipe cannot
accept all the requested bytes, splice_to_pipe() returns fewer bytes
than len, and 'len - copied' of data is effectively skipped over.

Fixes: e062fe9 ("tls: splice_read: fix accessing pre-processed records")
Link: https://patch.msgid.link/20260429222944.2139041-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/tls/tls_sw.c

@@ -2317,9 +2317,9 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 	if (copied < 0)
 		goto splice_requeue;
 
-	if (chunk < rxm->full_len) {
-		rxm->offset += len;
-		rxm->full_len -= len;
+	if (copied < rxm->full_len) {
+		rxm->offset += copied;
+		rxm->full_len -= copied;
 		goto splice_requeue;
 	}