netdev - Re: [PATCH] fib_trie: Fix potential null pointer dereference

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Date:	Sun, 7 Jun 2015 12:52:49 +0800
From:	Firo Yang <firogm@...il.com>
To:	walter harms <wharms@....de>
Cc:	davem@...emloft.net, kuznet@....inr.ac.ru, jmorris@...ei.org,
	yoshfuji@...ux-ipv6.org, kaber@...sh.net, netdev@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] fib_trie: Fix potential null pointer dereference

On Sat, Jun 06, 2015 at 03:39:38PM +0200, walter harms wrote:
>
>
>Am 06.06.2015 13:35, schrieb Firo Yang:
>> A smatch warning.
>> When kmem_cache_alloc() failed to alloc memory, a null pointer
>> will be returned. Redeference null pointer will generate
>> an unnecessary oops. So, use it after check.
>> 
>> Signed-off-by: Firo Yang <firogm@...il.com>
>> ---
>>  net/ipv4/fib_trie.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
>> index 01bce15..34094c7 100644
>> --- a/net/ipv4/fib_trie.c
>> +++ b/net/ipv4/fib_trie.c
>> @@ -326,12 +326,13 @@ static inline void empty_child_dec(struct key_vector *n)
>>  static struct key_vector *leaf_new(t_key key, struct fib_alias *fa)
>>  {
>>  	struct tnode *kv = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL);
>> -	struct key_vector *l = kv->kv;
>> +	struct key_vector *l;
>
>It is a good custom to have action and check close together, so this may be more
>obvious for future readers:
>	struct tnode *kv;
>	struct key_vector *l;
>
>        kv = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL);
>  	if (!kv)
>  		return NULL;
>
>
>re,
> wh
Thanks walter harms, I will update the patch like this.
>
>>  	/* initialize key vector */
>> +	l = kv->kv;
>>  	l->key = key;
>>  	l->pos = 0;
>>  	l->bits = 0;

-- 
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