Re: [dpdk-stable] [dpdk-dev] [PATCH] librte_flow_classify: fix out-of-bounds access

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 7/30/2019 4:43 PM, Aaron Conole wrote:
> Ferruh Yigit <ferruh.yigit@intel.com> writes:
> 
>> On 7/30/2019 3:42 PM, Aaron Conole wrote:
>>> David Marchand <david.marchand@redhat.com> writes:
>>>
>>>> On Wed, Jul 10, 2019 at 11:49 PM Thomas Monjalon <thomas@monjalon.net> wrote:
>>>>>
>>>>> 09/07/2019 13:09, Bernard Iremonger:
>>>>>> This patch fixes the out-of-bounds coverity issue by removing the
>>>>>> offending line of code at line 107 in rte_flow_classify_parse.c
>>>>>> which is never executed.
>>>>>>
>>>>>> Coverity issue: 343454
>>>>>>
>>>>>> Fixes: be41ac2a330f ("flow_classify: introduce flow classify library")
>>>>>> Cc: stable@dpdk.org
>>>>>> Signed-off-by: Bernard Iremonger <bernard.iremonger@intel.com>
>>>>>
>>>>> Applied, thanks
>>>>
>>>> We have a segfault in the unit tests since this patch.
>>>
>>> I think this patch is still correct.  The issue is in the semantic of
>>> the flow classify pattern.  It *MUST* always have a valid end marker,
>>> but the test passes an invalid end marker.  This causes the bounds to
>>> exceed.
>>>
>>> So, it would be best to fix it, either by having a "failure" on unknown
>>> markers (f.e. -1), or by passing a length around.  However, the crash
>>> should be expected.  The fact that the previous code was also incorrect
>>> and resulted in no segfault is pure luck.
>>>
>>> See rte_flow_classify_parse.c:80 and test_flow_classify.c:387
>>>
>>> I would be in favor of passing the lengths of the two arrays to these
>>> APIs.  That would let us still make use of the markers (for valid
>>> construction), but also let us reason about lengths in a sane way.
>>>
>>> WDYT?
>>>
>>
>> +1, I also just replied with something very similar.
>>
>> With current API the testcase is wrong, and it will crash, also the invalid
>> action one has exact same problem.
>>
>> The API can be updated as you suggested, with a length field and testcases can
>> be added back.
>>
>> What worries me more is the rte_flow, which uses same arguments, and open to
>> same errors, should we consider updating rte_flow APIs to have lengths values too?
> 
> Probably.
> 
> Here's a first crack at the change I think is appropriate.  I have done
> some limited testing.  Let me know if you want me to submit it formally.
> 
> ---------------------------- 8< ---------------------------------
> Subject: [PATCH] rte_flow_classify: fix up the API and preserve ABI
> 
> Introduces a new API for doing length validations, and preserves the old semantics
> and API.  The previous API couldn't handle corrupted end markers.  A future
> version of the API might be able to eschew the end marker and trust the length,
> but that is a discussion for future.
> 
> Signed-off-by: Aaron Conole <aconole@redhat.com>
> ---
>  app/test/test_flow_classify.c                | 30 +-------
>  lib/librte_flow_classify/rte_flow_classify.c | 72 +++++++++++++++++---
>  lib/librte_flow_classify/rte_flow_classify.h | 28 ++++++++
>  3 files changed, 91 insertions(+), 39 deletions(-)
> 
> diff --git a/app/test/test_flow_classify.c b/app/test/test_flow_classify.c
> index 6bbaad364..ff5265c6a 100644
> --- a/app/test/test_flow_classify.c
> +++ b/app/test/test_flow_classify.c
> @@ -125,7 +125,6 @@ static struct rte_flow_item  udp_item_bad = { RTE_FLOW_ITEM_TYPE_UDP,
>  
>  static struct rte_flow_item  end_item = { RTE_FLOW_ITEM_TYPE_END,
>  	0, 0, 0 };
> -static struct rte_flow_item  end_item_bad = { -1, 0, 0, 0 };
>  
>  /* test TCP pattern:
>   * "eth / ipv4 src spec 1.2.3.4 src mask 255.255.255.00 dst spec 5.6.7.8
> @@ -181,7 +180,6 @@ static struct rte_flow_action count_action = { RTE_FLOW_ACTION_TYPE_COUNT,
>  static struct rte_flow_action count_action_bad = { -1, 0};
>  
>  static struct rte_flow_action end_action = { RTE_FLOW_ACTION_TYPE_END, 0};
> -static struct rte_flow_action end_action_bad =	{ -1, 0};
>  
>  static struct rte_flow_action actions[2];
>  
> @@ -384,7 +382,7 @@ test_invalid_patterns(void)
>  
>  	pattern[1] = ipv4_udp_item_1;
>  	pattern[2] = udp_item_bad;
> -	pattern[3] = end_item_bad;
> +	pattern[3] = end_item;
>  
>  	ret = rte_flow_classify_validate(cls->cls, &attr, pattern,
>  			actions, &error);
> @@ -458,32 +456,6 @@ test_invalid_actions(void)
>  		return -1;
>  	}
>  
> -	actions[0] = count_action;
> -	actions[1] = end_action_bad;
> -
> -	ret = rte_flow_classify_validate(cls->cls, &attr, pattern,
> -			actions, &error);
> -	if (!ret) {
> -		printf("Line %i: rte_flow_classify_validate", __LINE__);
> -		printf(" should have failed!\n");
> -		return -1;
> -	}
> -
> -	rule = rte_flow_classify_table_entry_add(cls->cls, &attr, pattern,
> -			actions, &key_found, &error);
> -	if (rule) {
> -		printf("Line %i: flow_classify_table_entry_add", __LINE__);
> -		printf(" should have failed!\n");
> -		return -1;
> -	}
> -
> -	ret = rte_flow_classify_table_entry_delete(cls->cls, rule);
> -	if (!ret) {
> -		printf("Line %i: rte_flow_classify_table_entry_delete",
> -			__LINE__);
> -		printf("should have failed!\n");
> -		return -1;
> -	}
>  	return 0;
>  }

+1 to unit test updates, lgtm.

And I am for pushing the library updates to the next release, but please find a
few comments for now.


>  
> diff --git a/lib/librte_flow_classify/rte_flow_classify.c b/lib/librte_flow_classify/rte_flow_classify.c
> index 5ff585803..3ca1b1b44 100644
> --- a/lib/librte_flow_classify/rte_flow_classify.c
> +++ b/lib/librte_flow_classify/rte_flow_classify.c
> @@ -89,18 +89,51 @@ struct rte_flow_classify_rule {
>  	void *entry_ptr; /* handle to the table entry for rule meta data */
>  };
>  
> +static size_t
> +calc_flow_item_alen(const struct rte_flow_item pattern[])
> +{
> +	size_t i = 0;
> +	while (pattern && (pattern + i)->type != RTE_FLOW_ITEM_TYPE_END)
> +		i++;
> +	return i + 1;

I think better to send '0' if the pointer is NULL, (instead of 1)

<...>

> @@ -186,6 +186,34 @@ int
>  rte_flow_classify_table_create(struct rte_flow_classifier *cls,
>  		struct rte_flow_classify_table_params *params);
>  
> +/**
> + * Flow classify validate
> + *
> + * @param cls
> + *   Handle to flow classifier instance
> + * @param[in] attr
> + *   Flow rule attributes
> + * @param[in] pattern
> + *   Pattern specification (list terminated by the END pattern item).
> + * @param[in] actions
> + *   Associated actions (list terminated by the END pattern item).
> + * @param[out] error
> + *   Perform verbose error reporting if not NULL. Structure
> + *   initialised in case of error only.
> + * @return
> + *   0 on success, error code otherwise
> + */
> +__rte_experimental
> +int
> +rte_flow_classify_validate_l(struct rte_flow_classifier *cls,
> +			     const struct rte_flow_attr *attr,
> +			     const struct rte_flow_item pattern[],
> +			     const size_t pattern_l,
> +			     const struct rte_flow_action actions[],
> +			     const size_t actions_l,
> +			     struct rte_flow_error *error);

The doxygen comment is missing for 'pattern_l' & 'actions_l' but from code it is
number of items in the lists, this is duplication of the END marker information.
Instead, if those lengths are the length of the arrays will it be easier for the
user? So user won't need to calculate the item count but can pass the size of
the array. This still prevents API access out of the array.

Anyway, as suggested above lets not make these decisions just a few days before
the release, but just get the unit test fix for the release, does it make sense?

And if so, can you send the unit test patch?

Thanks,
ferruh