From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: dev@dpdk.org, Maxime Coquelin <maxime.coquelin@redhat.com>
Subject: Re: [dpdk-dev] [PATCH] net/virtio-user: fix cannot get initialized
Date: Thu, 13 Apr 2017 15:37:22 +0800 [thread overview]
Message-ID: <26fc0c02-ce9d-53ae-656e-2a278dc85867@intel.com> (raw)
In-Reply-To: <20170413022128.GG7333@yliu-dev.sh.intel.com>
On 4/13/2017 10:21 AM, Yuanhan Liu wrote:
> On Thu, Apr 13, 2017 at 10:18:43AM +0800, Tan, Jianfeng wrote:
>>
>> 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 <maxime.coquelin@redhat.com>
>>>> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
>>>>
>>>> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
>>>> ---
>>>> 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.
> If so, fix it in another patch, with the detailed (and real) errors in
> the commit log.
>
OK, I'll drop this fix from this patch.
next prev parent reply other threads:[~2017-04-13 7:37 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-07 7:57 Jianfeng Tan
2017-04-13 1:58 ` Yuanhan Liu
2017-04-13 2:18 ` Tan, Jianfeng
2017-04-13 2:21 ` Yuanhan Liu
2017-04-13 7:37 ` Tan, Jianfeng [this message]
2017-04-13 2:36 ` Yuanhan Liu
2017-04-13 7:39 ` Tan, Jianfeng
2017-04-13 10:11 ` [dpdk-dev] [PATCH v2] " Jianfeng Tan
2017-04-14 4:24 ` Yuanhan Liu
2017-04-14 4:35 ` Tan, Jianfeng
2017-04-14 5:37 ` Yuanhan Liu
2017-04-14 5:55 ` Tan, Jianfeng
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