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SubjectRe: [PATCH v3 1/2] Make loop indexes unsigned
On 2023-09-28 06:40, Pablo Neira Ayuso wrote:
> On Wed, Sep 27, 2023 at 09:47:14AM -0700, joao@overdrivepizza.com
> wrote:
>> From: Joao Moreira <joao.moreira@intel.com>
>>
>> Both flow_rule_alloc and offload_action_alloc functions received an
>> unsigned num_actions parameters which are then operated within a loop.
>> The index of this loop is declared as a signed int. If it was possible
>> to pass a large enough num_actions to these functions, it would lead
>> to
>> an out of bounds write.
>>
>> After checking with maintainers, it was mentioned that front-end will
>> cap the num_actions value and that it is not possible to reach this
>> function with such a large number. Yet, for correctness, it is still
>> better to fix this.
>>
>> This issue was observed by the commit author while reviewing a
>> write-up
>> regarding a CVE within the same subsystem [1].
>>
>> 1 - https://nickgregory.me/post/2022/03/12/cve-2022-25636/
>>
>> Signed-off-by: Joao Moreira <joao.moreira@intel.com>
>> ---
>> net/core/flow_offload.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
>> index bc5169482710..bc3f53a09d8f 100644
>> --- a/net/core/flow_offload.c
>> +++ b/net/core/flow_offload.c
>> @@ -10,7 +10,7 @@
>> struct flow_rule *flow_rule_alloc(unsigned int num_actions)
>> {
>> struct flow_rule *rule;
>> - int i;
>> + unsigned int i;
>
> With the 2^8 cap, I don't think this patch is required anymore.

Hm. While I understand that there is not a significant menace haunting
this... would it be good for (1) type correctness and (2) prevent that
things blow up if something changes and someone misses this spot?

>
>>
>> rule = kzalloc(struct_size(rule, action.entries, num_actions),
>> GFP_KERNEL);
>> @@ -31,7 +31,7 @@ EXPORT_SYMBOL(flow_rule_alloc);
>> struct flow_offload_action *offload_action_alloc(unsigned int
>> num_actions)
>> {
>> struct flow_offload_action *fl_action;
>> - int i;
>> + unsigned int i;
>>
>> fl_action = kzalloc(struct_size(fl_action, action.entries,
>> num_actions),
>> GFP_KERNEL);
>> --
>> 2.42.0
>>

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