On 4/13/2017 9:58 AM, Yuanhan Liu wrote:
On Fri, Apr 07, 2017 at 07:57:40AM +0000, Jianfeng Tan wrote:After the introduction of vhost MTU, VIRTIO_NET_F_MTU is enabled by default. However, virtio-user vtpci does not support to get MTU from device yet, i.e., vtpci_read_dev_config(MTU) fails. Plus, struct virtio_net_config is defined as a uninitialized variable, and could be different values in virtio_negotiate_features() and virtio_init_device(). In some cases, it passes the check in virtio_negotiate_features() but fails the check in virtio_init_device(). As a result, virtio-user canno be initialized. To fix it, (1) accessing uninitialized variable is not a good practice, so initialize it as zero; (2) explicitly disable MTU feature in virtio-user. Fixes: 49d26d9e3f47 ("net/virtio: support MTU feature") Cc: Maxime Coquelin <[email protected]> Cc: Yuanhan Liu <[email protected]> Signed-off-by: Jianfeng Tan <[email protected]> --- drivers/net/virtio/virtio_ethdev.c | 4 ++-- drivers/net/virtio/virtio_user/virtio_user_dev.c | 6 ++++++ 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c index 78cb3e8..4c43784 100644 --- a/drivers/net/virtio/virtio_ethdev.c +++ b/drivers/net/virtio/virtio_ethdev.c @@ -1163,7 +1163,7 @@ virtio_negotiate_features(struct virtio_hw *hw, uint64_t req_features)/* If supported, ensure MTU value is valid before acknowledging it. */if (host_features & req_features & (1ULL << VIRTIO_NET_F_MTU)) { - struct virtio_net_config config; + struct virtio_net_config config = {0};virtio-user does not support the MTU feature, this patch should not be reached. The virtio-user feature negotiation should be broken. --yliu
Yes, it will not come to here anyway. But some static code analyzer might report this as an error: there's chance to read uninitialized variable.
Thanks, Jianfeng
