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    Subject[PATCH AUTOSEL for 4.9 193/293] datapath: Avoid using stack larger than 1024.
    Date
    From: Tonghao Zhang <xiangxia.m.yue@gmail.com>

    [ Upstream commit 9cc9a5cb176ccb4f2cda5ac34da5a659926f125f ]

    When compiling OvS-master on 4.4.0-81 kernel,
    there is a warning:

    CC [M] /root/ovs/datapath/linux/datapath.o
    /root/ovs/datapath/linux/datapath.c: In function
    'ovs_flow_cmd_set':
    /root/ovs/datapath/linux/datapath.c:1221:1: warning:
    the frame size of 1040 bytes is larger than 1024 bytes
    [-Wframe-larger-than=]

    This patch factors out match-init and action-copy to avoid
    "Wframe-larger-than=1024" warning. Because mask is only
    used to get actions, we new a function to save some
    stack space.

    Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
    Acked-by: Pravin B Shelar <pshelar@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    net/openvswitch/datapath.c | 81 +++++++++++++++++++++++++++++++++-------------
    1 file changed, 58 insertions(+), 23 deletions(-)

    diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
    index 453f806afe6e..0f594140c5ff 100644
    --- a/net/openvswitch/datapath.c
    +++ b/net/openvswitch/datapath.c
    @@ -1105,6 +1105,58 @@ static struct sw_flow_actions *get_flow_actions(struct net *net,
    return acts;
    }

    +/* Factor out match-init and action-copy to avoid
    + * "Wframe-larger-than=1024" warning. Because mask is only
    + * used to get actions, we new a function to save some
    + * stack space.
    + *
    + * If there are not key and action attrs, we return 0
    + * directly. In the case, the caller will also not use the
    + * match as before. If there is action attr, we try to get
    + * actions and save them to *acts. Before returning from
    + * the function, we reset the match->mask pointer. Because
    + * we should not to return match object with dangling reference
    + * to mask.
    + * */
    +static int ovs_nla_init_match_and_action(struct net *net,
    + struct sw_flow_match *match,
    + struct sw_flow_key *key,
    + struct nlattr **a,
    + struct sw_flow_actions **acts,
    + bool log)
    +{
    + struct sw_flow_mask mask;
    + int error = 0;
    +
    + if (a[OVS_FLOW_ATTR_KEY]) {
    + ovs_match_init(match, key, true, &mask);
    + error = ovs_nla_get_match(net, match, a[OVS_FLOW_ATTR_KEY],
    + a[OVS_FLOW_ATTR_MASK], log);
    + if (error)
    + goto error;
    + }
    +
    + if (a[OVS_FLOW_ATTR_ACTIONS]) {
    + if (!a[OVS_FLOW_ATTR_KEY]) {
    + OVS_NLERR(log,
    + "Flow key attribute not present in set flow.");
    + return -EINVAL;
    + }
    +
    + *acts = get_flow_actions(net, a[OVS_FLOW_ATTR_ACTIONS], key,
    + &mask, log);
    + if (IS_ERR(*acts)) {
    + error = PTR_ERR(*acts);
    + goto error;
    + }
    + }
    +
    + /* On success, error is 0. */
    +error:
    + match->mask = NULL;
    + return error;
    +}
    +
    static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
    {
    struct net *net = sock_net(skb->sk);
    @@ -1112,7 +1164,6 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
    struct ovs_header *ovs_header = info->userhdr;
    struct sw_flow_key key;
    struct sw_flow *flow;
    - struct sw_flow_mask mask;
    struct sk_buff *reply = NULL;
    struct datapath *dp;
    struct sw_flow_actions *old_acts = NULL, *acts = NULL;
    @@ -1124,34 +1175,18 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
    bool ufid_present;

    ufid_present = ovs_nla_get_ufid(&sfid, a[OVS_FLOW_ATTR_UFID], log);
    - if (a[OVS_FLOW_ATTR_KEY]) {
    - ovs_match_init(&match, &key, true, &mask);
    - error = ovs_nla_get_match(net, &match, a[OVS_FLOW_ATTR_KEY],
    - a[OVS_FLOW_ATTR_MASK], log);
    - } else if (!ufid_present) {
    + if (!a[OVS_FLOW_ATTR_KEY] && !ufid_present) {
    OVS_NLERR(log,
    "Flow set message rejected, Key attribute missing.");
    - error = -EINVAL;
    + return -EINVAL;
    }
    +
    + error = ovs_nla_init_match_and_action(net, &match, &key, a,
    + &acts, log);
    if (error)
    goto error;

    - /* Validate actions. */
    - if (a[OVS_FLOW_ATTR_ACTIONS]) {
    - if (!a[OVS_FLOW_ATTR_KEY]) {
    - OVS_NLERR(log,
    - "Flow key attribute not present in set flow.");
    - error = -EINVAL;
    - goto error;
    - }
    -
    - acts = get_flow_actions(net, a[OVS_FLOW_ATTR_ACTIONS], &key,
    - &mask, log);
    - if (IS_ERR(acts)) {
    - error = PTR_ERR(acts);
    - goto error;
    - }
    -
    + if (acts) {
    /* Can allocate before locking if have acts. */
    reply = ovs_flow_cmd_alloc_info(acts, &sfid, info, false,
    ufid_flags);
    --
    2.15.1
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