On Wed, 10 Jan 2024 14:01:23 -0800 John Fastabend wrote: > 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. Reviewed-by: Jakub Kicinski <kuba@xxxxxxxxxx>
