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    SubjectRE: [PATCH] netlink: don't copy over empty attribute data
    Date
    From: Sasha Levin
    > netlink uses empty data to seperate different levels. However, we still
    > try to copy that data from a NULL ptr using memcpy, which is an undefined
    > behaviour.
    >
    > Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
    > ---
    > lib/nlattr.c | 3 ++-
    > 1 file changed, 2 insertions(+), 1 deletion(-)
    >
    > diff --git a/lib/nlattr.c b/lib/nlattr.c
    > index 9c3e85f..6512b43 100644
    > --- a/lib/nlattr.c
    > +++ b/lib/nlattr.c
    > @@ -430,7 +430,8 @@ void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
    > struct nlattr *nla;
    >
    > nla = __nla_reserve(skb, attrtype, attrlen);
    > - memcpy(nla_data(nla), data, attrlen);
    > + if (data)
    > + memcpy(nla_data(nla), data, attrlen);

    Were it even appropriate to add a conditional here, the correct
    check would be against 'attrlen', not 'data'.

    David

    > }
    > EXPORT_SYMBOL(__nla_put);
    >
    > --
    > 1.7.10.4
    >
    > --
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