On Wed, 28 Jun 2017, Greg Kurz wrote:
> Contrary to what is written in the comment, a buggy guest can misconfigure
> the transport buffers and pdu_marshal() may return an error. If this ever
> happens, it is up to the transport layer to handle the situation (9P is
> transport agnostic).
>
> This fixes Coverity issue CID1348518.
>
> Signed-off-by: Greg Kurz <gr...@kaod.org>
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
> ---
> hw/9pfs/9p.c | 23 +++++++++++++++--------
> 1 file changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index da0d6da65b45..f7871e6f3e5a 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -624,15 +624,11 @@ void pdu_free(V9fsPDU *pdu)
> QLIST_INSERT_HEAD(&s->free_list, pdu, next);
> }
>
> -/*
> - * We don't do error checking for pdu_marshal/unmarshal here
> - * because we always expect to have enough space to encode
> - * error details
> - */
> static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
> {
> int8_t id = pdu->id + 1; /* Response */
> V9fsState *s = pdu->s;
> + int ret;
>
> if (len < 0) {
> int err = -len;
> @@ -644,11 +640,19 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu,
> ssize_t len)
> str.data = strerror(err);
> str.size = strlen(str.data);
>
> - len += pdu_marshal(pdu, len, "s", &str);
> + ret = pdu_marshal(pdu, len, "s", &str);
> + if (ret < 0) {
> + goto out_notify;
> + }
> + len += ret;
> id = P9_RERROR;
> }
>
> - len += pdu_marshal(pdu, len, "d", err);
> + ret = pdu_marshal(pdu, len, "d", err);
> + if (ret < 0) {
> + goto out_notify;
> + }
> + len += ret;
>
> if (s->proto_version == V9FS_PROTO_2000L) {
> id = P9_RLERROR;
> @@ -657,12 +661,15 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu,
> ssize_t len)
> }
>
> /* fill out the header */
> - pdu_marshal(pdu, 0, "dbw", (int32_t)len, id, pdu->tag);
> + if (pdu_marshal(pdu, 0, "dbw", (int32_t)len, id, pdu->tag) < 0) {
> + goto out_notify;
> + }
>
> /* keep these in sync */
> pdu->size = len;
> pdu->id = id;
>
> +out_notify:
> pdu->s->transport->push_and_notify(pdu);
>
> /* Now wakeup anybody waiting in flush for this request */
>
