linux-kernel - Re: [PATCH] netlink: Fix kfree NULL pointer

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Date:	Wed, 8 Sep 2010 13:33:28 +0800
From:	jovi zhang <bookjovi@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Johannes Berg <johannes.berg@...el.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...nvz.org>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] netlink: Fix kfree NULL pointer

On Wed, Sep 8, 2010 at 1:19 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le mercredi 08 septembre 2010 à 13:13 +0800, jovi zhang a écrit :
>> It will kfree NULL pointer if listeners is NULL. fix it.
>>
>> Signed-off-by: bookjovi@...il.com
>> net/netlink/af_netlink.c |    5 +++--
>> 1 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
>> index 980fe4a..1c7bf48 100644
>> --- a/net/netlink/af_netlink.c
>> +++ b/net/netlink/af_netlink.c
>> @@ -1532,8 +1532,10 @@ netlink_kernel_create(struct net *net, int
>> unit, unsigned int groups,
>>        if (input)
>>                nlk_sk(sk)->netlink_rcv = input;
>>
>> -       if (netlink_insert(sk, net, 0))
>> +       if (netlink_insert(sk, net, 0)) {
>> +               kfree(listeners);
>>                goto out_sock_release;
>> +       }
>>
>>        nlk = nlk_sk(sk);
>>        nlk->flags |= NETLINK_KERNEL_SOCKET;
>> @@ -1553,7 +1555,6 @@ netlink_kernel_create(struct net *net, int unit,
>> unsigned int groups,
>>        return sk;
>>
>> out_sock_release:
>> -       kfree(listeners);
>>        netlink_kernel_release(sk);
>>        return NULL;
>
>
> This patch is not needed
>
> kfree(NULL) is legal
>
>
>
>

YES, maybe kfree(NULL) is legal, but I cannot see there have any need
to invoke kfree(NULL) in this function.
 Also I check kfree usage in other code, I havn't find any kfree(NULL) usage.
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