From: David Miller <davem@davemloft.net>
To: edumazet@google.com
Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com,
syzkaller@googlegroups.com, maximmi@mellanox.com
Subject: Re: [PATCH net] ipv6/addrconf: fix potential NULL deref in inet6_set_link_af()
Date: Thu, 06 Feb 2020 14:13:00 +0100 (CET) [thread overview]
Message-ID: <20200206.141300.1752448469848126511.davem@davemloft.net> (raw)
In-Reply-To: <20200205165544.242623-1-edumazet@google.com>
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 5 Feb 2020 08:55:44 -0800
> __in6_dev_get(dev) called from inet6_set_link_af() can return NULL.
>
> The needed check has been recently removed, let's add it back.
I am having trouble understanding this one.
When we have a do_setlink operation the flow is that we first validate
the AFs and then invoke setlink operations after that validation.
do_setlink() {
..
err = validate_linkmsg(dev, tb);
if (err < 0)
return err;
..
if (tb[IFLA_AF_SPEC]) {
...
err = af_ops->set_link_af(dev, af);
if (err < 0) {
rcu_read_unlock();
goto errout;
}
By definition, we only get to ->set_link_af() if there is an
IFLA_AF_SPEC nested attribute and if we look at the validation
performed by validate_linkmsg() it goes:
if (tb[IFLA_AF_SPEC]) {
...
if (af_ops->validate_link_af) {
err = af_ops->validate_link_af(dev, af);
...
And validate_link_af in net/ipv6/addrconf.c clearly does the
following:
static int inet6_validate_link_af(const struct net_device *dev,
const struct nlattr *nla)
...
if (dev) {
idev = __in6_dev_get(dev);
if (!idev)
return -EAFNOSUPPORT;
}
...
It checks the idev and makes sure it is not-NULL.
I therefore cannot find a path by which we arrive at inet6_set_link_af
with a NULL idev. The above validation code should trap it.
Please explain.
Thank you.
next prev parent reply other threads:[~2020-02-06 13:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-05 16:55 [PATCH net] ipv6/addrconf: fix potential NULL deref in inet6_set_link_af() Eric Dumazet
2020-02-06 13:13 ` David Miller [this message]
2020-02-06 15:18 ` Eric Dumazet
2020-02-07 2:50 ` Eric Dumazet
2020-02-07 9:36 ` David Miller
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