From: Jiri Slaby <jslaby@suse.cz>
To: Gen Zhang <blackgod016574@gmail.com>,
davem@davemloft.net, kuznet@ms2.inr.ac.ru,
yoshfuji@linux-ipv6.org
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ipv6_sockglue: Fix a missing-check bug in ip6_ra_control()
Date: Mon, 1 Jul 2019 10:57:36 +0200 [thread overview]
Message-ID: <1b5f82ae-31a7-db36-dc9d-efc46cda2af3@suse.cz> (raw)
In-Reply-To: <20190524031946.GA6463@zhanggen-UX430UQ>
On 24. 05. 19, 5:19, Gen Zhang wrote:
> In function ip6_ra_control(), the pointer new_ra is allocated a memory
> space via kmalloc(). And it is used in the following codes. However,
> when there is a memory allocation error, kmalloc() fails. Thus null
> pointer dereference may happen. And it will cause the kernel to crash.
> Therefore, we should check the return value and handle the error.
>
> Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
>
> ---
> diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
> index 40f21fe..0a3d035 100644
> --- a/net/ipv6/ipv6_sockglue.c
> +++ b/net/ipv6/ipv6_sockglue.c
> @@ -68,6 +68,8 @@ int ip6_ra_control(struct sock *sk, int sel)
> return -ENOPROTOOPT;
>
> new_ra = (sel >= 0) ? kmalloc(sizeof(*new_ra), GFP_KERNEL) : NULL;
> + if (sel >= 0 && !new_ra)
> + return -ENOMEM;
>
> write_lock_bh(&ip6_ra_lock);
> for (rap = &ip6_ra_chain; (ra = *rap) != NULL; rap = &ra->next) {
>
Was this really an omission? There is (!new_ra) handling below the for loop:
if (!new_ra) {
write_unlock_bh(&ip6_ra_lock);
return -ENOBUFS;
}
It used to handle both (sel >= 0) and (sel == 0) cases and it used to
return ENOBUFS in case of failure. For (sel >= 0) it also could at least
return EADDRINUSE when a collision was found -- even if memory was
exhausted.
In anyway, how could this lead to a pointer dereference? And why/how did
this get a CVE number?
thanks,
--
js
suse labs
next prev parent reply other threads:[~2019-07-01 8:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-24 3:19 [PATCH] ipv6_sockglue: Fix a missing-check bug in ip6_ra_control() Gen Zhang
2019-05-25 18:00 ` David Miller
2019-07-01 8:57 ` Jiri Slaby [this message]
2019-07-01 9:06 ` Gen Zhang
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