[PATCH] netfilter: fix possible ZERO_SIZE_PTR pointer dereferencing error.

[PATCH] netfilter: fix possible ZERO_SIZE_PTR pointer dereferencing error.

[Xiubo Li]

Since we cannot make sure the 'hook_mask' will always be none zero
here. If it equals to zero, the num_hooks will be zero too, and then
kmalloc() will return ZERO_SIZE_PTR, which is (void *)16.

Then the following error check will fails:
  ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
  if (ops == NULL)
          return ERR_PTR(-ENOMEM);

So this patch fix this with just doing the zero check before calling
kmalloc() is called.

Maybe the case above will never happen here, but in theory.

Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
---
 net/netfilter/x_tables.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index c8a0b7d..4df8e38 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)
 	struct nf_hook_ops *ops;
 	int ret;
 
+	if (!num_hooks)
+		return ERR_PTR(-EINVAL);
+
 	ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
 	if (ops == NULL)
 		return ERR_PTR(-ENOMEM);
-- 
1.8.3.1

Re: [PATCH] netfilter: fix possible ZERO_SIZE_PTR pointer dereferencing error.

[Pablo Neira Ayuso]

On Wed, Jun 01, 2016 at 04:34:28PM +0800, Xiubo Li wrote:
> Since we cannot make sure the 'hook_mask' will always be none zero
> here. If it equals to zero, the num_hooks will be zero too, and then
> kmalloc() will return ZERO_SIZE_PTR, which is (void *)16.
> 
> Then the following error check will fails:
>   ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
>   if (ops == NULL)
>           return ERR_PTR(-ENOMEM);
> 
> So this patch fix this with just doing the zero check before calling
> kmalloc() is called.
> 
> Maybe the case above will never happen here, but in theory.
> 
> Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
> ---
>  net/netfilter/x_tables.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index c8a0b7d..4df8e38 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)

What kernel version are you using? I don't see xt_hook_link() in the
development tree.

>  	struct nf_hook_ops *ops;
>  	int ret;
>  
> +	if (!num_hooks)
> +		return ERR_PTR(-EINVAL);
> +
>  	ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
>  	if (ops == NULL)
>  		return ERR_PTR(-ENOMEM);
> -- 
> 1.8.3.1
> 
> 
> 

Re: [PATCH] netfilter: fix possible ZERO_SIZE_PTR pointerdereferencing error.

[Xiubo Li]

>>   net/netfilter/x_tables.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
>> index c8a0b7d..4df8e38 100644
>> --- a/net/netfilter/x_tables.c
>> +++ b/net/netfilter/x_tables.c
>> @@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)
>
> What kernel version are you using? I don't see xt_hook_link() in the
> development tree.

Sorry, in the wrong tree, i just work on linux-next tree, forget to 
checkout the newest tags.

Should I will use nf.git tree or others instead ?

>


Thanks very much.

BRs
Xiubo Li

Re: [PATCH] netfilter: fix possible ZERO_SIZE_PTR pointerdereferencing error.

[Pablo Neira Ayuso]

On Wed, Jun 01, 2016 at 05:52:59PM +0800, Xiubo Li wrote:
> >>  net/netfilter/x_tables.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >>diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> >>index c8a0b7d..4df8e38 100644
> >>--- a/net/netfilter/x_tables.c
> >>+++ b/net/netfilter/x_tables.c
> >>@@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)
> >
> >What kernel version are you using? I don't see xt_hook_link() in the
> >development tree.
> 
> Sorry, in the wrong tree, i just work on linux-next tree, forget to checkout
> the newest tags.
> 
> Should I will use nf.git tree or others instead ?

Yes please, thanks.

Re: [PATCH] netfilter: fix possible ZERO_SIZE_PTRpointerdereferencing error.

[Xiubo Li]

On 01/06/2016 19:04, Pablo Neira Ayuso wrote:
> On Wed, Jun 01, 2016 at 05:52:59PM +0800, Xiubo Li wrote:
>>>>   net/netfilter/x_tables.c | 3 +++
>>>>   1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
>>>> index c8a0b7d..4df8e38 100644
>>>> --- a/net/netfilter/x_tables.c
>>>> +++ b/net/netfilter/x_tables.c
>>>> @@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)
>>>
>>> What kernel version are you using? I don't see xt_hook_link() in the
>>> development tree.
>>
>> Sorry, in the wrong tree, i just work on linux-next tree, forget to checkout
>> the newest tags.
>>
>> Should I will use nf.git tree or others instead ?
>
> Yes please, thanks.
>

Okay.

Thanks,

BRs
Xiubo Li