Re: [Xen-devel] [PATCH] xen-netback: correct return value checks on xenbus_scanf()

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Jan
> Beulich
> Sent: 07 July 2016 08:57
> To: Wei Liu
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> Subject: [Xen-devel] [PATCH] xen-netback: correct return value checks on
> xenbus_scanf()
> 
> Only a positive return value indicates success.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> ---
>  drivers/net/xen-netback/xenbus.c |   26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> --- 4.7-rc6-xenbus_scanf.orig/drivers/net/xen-netback/xenbus.c
> +++ 4.7-rc6-xenbus_scanf/drivers/net/xen-netback/xenbus.c
> @@ -741,7 +741,7 @@ static void xen_mcast_ctrl_changed(struc
>       int val;
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend,
> -                      "request-multicast-control", "%d", &val) < 0)
> +                      "request-multicast-control", "%d", &val) <= 0)
>               val = 0;
>       vif->multicast_control = !!val;
>  }
> @@ -890,7 +890,7 @@ static void connect(struct backend_info
>       err = xenbus_scanf(XBT_NIL, dev->otherend,
>                          "multi-queue-num-queues",
>                          "%u", &requested_num_queues);
> -     if (err < 0) {
> +     if (err <= 0) {
>               requested_num_queues = 1; /* Fall back to single queue */
>       } else if (requested_num_queues > xenvif_max_queues) {
>               /* buggy or malicious guest */
> @@ -1056,7 +1056,7 @@ static int connect_data_rings(struct bac
>       if (err < 0) {
>               err = xenbus_scanf(XBT_NIL, xspath,
>                                  "event-channel", "%u", &tx_evtchn);
> -             if (err < 0) {
> +             if (err <= 0) {
>                       xenbus_dev_fatal(dev, err,
>                                        "reading %s/event-channel(-tx/rx)",
>                                        xspath);
> @@ -1092,10 +1092,10 @@ static int read_xenbus_vif_flags(struct
>       err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy",
> "%u",
>                          &rx_copy);
>       if (err == -ENOENT) {
> -             err = 0;
> +             err = 1;
>               rx_copy = 0;
>       }
> -     if (err < 0) {
> +     if (err <= 0) {
>               xenbus_dev_fatal(dev, err, "reading %s/request-rx-copy",
>                                dev->otherend);
>               return err;
> @@ -1104,7 +1104,7 @@ static int read_xenbus_vif_flags(struct
>               return -EOPNOTSUPP;
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend,
> -                      "feature-rx-notify", "%d", &val) < 0)
> +                      "feature-rx-notify", "%d", &val) <= 0)
>               val = 0;
>       if (!val) {
>               /* - Reduce drain timeout to poll more frequently for
> @@ -1116,7 +1116,7 @@ static int read_xenbus_vif_flags(struct
>       }
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg",
> -                      "%d", &val) < 0)
> +                      "%d", &val) <= 0)
>               val = 0;
>       vif->can_sg = !!val;
> 
> @@ -1124,25 +1124,25 @@ static int read_xenbus_vif_flags(struct
>       vif->gso_prefix_mask = 0;
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4",
> -                      "%d", &val) < 0)
> +                      "%d", &val) <= 0)
>               val = 0;
>       if (val)
>               vif->gso_mask |= GSO_BIT(TCPV4);
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4-
> prefix",
> -                      "%d", &val) < 0)
> +                      "%d", &val) <= 0)
>               val = 0;
>       if (val)
>               vif->gso_prefix_mask |= GSO_BIT(TCPV4);
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6",
> -                      "%d", &val) < 0)
> +                      "%d", &val) <= 0)
>               val = 0;
>       if (val)
>               vif->gso_mask |= GSO_BIT(TCPV6);
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6-
> prefix",
> -                      "%d", &val) < 0)
> +                      "%d", &val) <= 0)
>               val = 0;
>       if (val)
>               vif->gso_prefix_mask |= GSO_BIT(TCPV6);
> @@ -1156,12 +1156,12 @@ static int read_xenbus_vif_flags(struct
>       }
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-
> offload",
> -                      "%d", &val) < 0)
> +                      "%d", &val) <= 0)
>               val = 0;
>       vif->ip_csum = !val;
> 
>       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-
> offload",
> -                      "%d", &val) < 0)
> +                      "%d", &val) <= 0)
>               val = 0;
>       vif->ipv6_csum = !!val;
> 
> 
> 
> 
> 
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