Re: [dpdk-dev] [PATCH] service: don't walk out of bounds when checking services

[Aaron Conole <aconole@redhat.com>]

David Marchand <david.marchand@redhat.com> writes:

> On Tue, Nov 26, 2019 at 3:56 PM Aaron Conole <aconole@redhat.com> wrote:
>>
>> The service_valid call is used without properly bounds checking the
>> input parameter.  Almost all instances of the service_valid call are
>> inside a for() loop that prevents excessive walks, but some of the
>> public APIs don't bounds check and will pass invalid arguments.
>>
>> Prevent this by using SERVICE_GET_OR_ERR_RET where it makes sense,
>> and adding a bounds check to one service_valid() use.
>>
>> Fixes: 8d39d3e237c2 ("service: fix race in service on app lcore function")
>> Fixes: e9139a32f6e8 ("service: add function to run on app lcore")
>> Fixes: e30dd31847d2 ("service: add mechanism for quiescing")
>> Signed-off-by: Aaron Conole <aconole@redhat.com>
>> ---
>>  lib/librte_eal/common/rte_service.c | 23 +++++++++++------------
>>  1 file changed, 11 insertions(+), 12 deletions(-)
>>
>> diff --git a/lib/librte_eal/common/rte_service.c b/lib/librte_eal/common/rte_service.c
>> index 79235c03f8..73de7bbade 100644
>> --- a/lib/librte_eal/common/rte_service.c
>> +++ b/lib/librte_eal/common/rte_service.c
>> @@ -345,11 +345,12 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,
>>
>>
>>  static inline int32_t
>> -service_run(uint32_t i, struct core_state *cs, uint64_t service_mask)
>> +service_run(uint32_t i, struct core_state *cs, uint64_t service_mask,
>> +           struct rte_service_spec_impl *s)
>>  {
>> -       if (!service_valid(i))
>> -               return -EINVAL;
>> -       struct rte_service_spec_impl *s = &rte_services[i];
>> +       if (!s)
>> +               SERVICE_VALID_GET_OR_ERR_RET(i, s, -EINVAL);
>> +
>
> No need to check the service if we ensure that the passed index is valid.
> See below.

Okay.  I will document that then ;)

>
>>         if (s->comp_runstate != RUNSTATE_RUNNING ||
>>                         s->app_runstate != RUNSTATE_RUNNING ||
>>                         !(service_mask & (UINT64_C(1) << i))) {
>> @@ -383,7 +384,7 @@ rte_service_may_be_active(uint32_t id)
>>         int32_t lcore_count = rte_service_lcore_list(ids, RTE_MAX_LCORE);
>>         int i;
>>
>> -       if (!service_valid(id))
>> +       if (id >= RTE_SERVICE_NUM_MAX || !service_valid(id))
>>                 return -EINVAL;
>>
>>         for (i = 0; i < lcore_count; i++) {
>> @@ -397,12 +398,10 @@ rte_service_may_be_active(uint32_t id)
>>  int32_t
>>  rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t serialize_mt_unsafe)
>>  {
>> -       /* run service on calling core, using all-ones as the service mask */
>> -       if (!service_valid(id))
>> -               return -EINVAL;
>> -
>>         struct core_state *cs = &lcore_states[rte_lcore_id()];
>> -       struct rte_service_spec_impl *s = &rte_services[id];
>> +       struct rte_service_spec_impl *s;
>> +
>> +       SERVICE_VALID_GET_OR_ERR_RET(id, s, -EINVAL);
>>
>>         /* Atomically add this core to the mapped cores first, then examine if
>>          * we can run the service. This avoids a race condition between
>> @@ -418,7 +417,7 @@ rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t serialize_mt_unsafe)
>>                 return -EBUSY;
>>         }
>>
>> -       int ret = service_run(id, cs, UINT64_MAX);
>> +       int ret = service_run(id, cs, UINT64_MAX, s);
>>
>>         if (serialize_mt_unsafe)
>>                 rte_atomic32_dec(&s->num_mapped_cores);
>> @@ -439,7 +438,7 @@ rte_service_runner_func(void *arg)
>>
>>                 for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) {
>>                         /* return value ignored as no change to code flow */
>
> if (!service_valid(idx))
>     continue;
>
> Plus, if we add this check here, thenall loops in this file are consistent.
> WDYT?

Agreed - it's better.  Okay.