A splice with MSG_SPLICE_PAGES will cause tls code to use the
tls_sw_sendmsg_splice path in the TLS sendmsg code to move the user
provided pages from the msg into the msg_pl. This will loop over the
msg until msg_pl is full, checked by sk_msg_full(msg_pl). The user
can also set the MORE flag to hint stack to delay sending until receiving
more pages and ideally a full buffer.
If the user adds more pages to the msg than can fit in the msg_pl
scatterlist (MAX_MSG_FRAGS) we should ignore the MORE flag and send
the buffer anyways.
What actually happens though is we abort the msg to msg_pl scatterlist
setup and then because we forget to set 'full record' indicating we
can no longer consume data without a send we fallthrough to the 'continue'
path which will check if msg_data_left(msg) has more bytes to send and
then attempts to fit them in the already full msg_pl. Then next
iteration of sender doing send will encounter a full msg_pl and throw
the warning in the syzbot report.
To fix simply check if we have a full_record in splice code path and
if not send the msg regardless of MORE flag.
Reported-and-tested-by: syzbot+f2977222e0e95cec15c8@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: Edward Adam Davis <eadavis@xxxxxx>
Fixes: fe1e81d4f73b ("tls/sw: Support MSG_SPLICE_PAGES")
Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
---
net/tls/tls_sw.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index e37b4d2e2acd..31e8a94dfc11 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1052,7 +1052,11 @@ static int tls_sw_sendmsg_locked(struct sock *sk, struct msghdr *msg,
if (ret < 0)
goto send_end;
tls_ctx->pending_open_record_frags = true;
- if (full_record || eor || sk_msg_full(msg_pl))
+
+ if (sk_msg_full(msg_pl))
+ full_record = true;
+
+ if (full_record || eor)
goto copied;
continue;
}
--
2.33.0
