Re: [dpdk-dev] [PATCH] lpm: fix unchecked return value

["Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>]

Hi Ruifeng,

On 16/07/2020 06:19, Ruifeng Wang wrote:
> Coverity complains about unchecked return value of rte_rcu_qsbr_dq_enqueue.
> By default, defer queue size is big enough to hold all tbl8 groups. When
> enqueue fails, return error to the user to indicate system issue.
> 
> Coverity issue: 360832
> Fixes: 8a9f8564e9f9 ("lpm: implement RCU rule reclamation")
> 
> Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>   lib/librte_lpm/rte_lpm.c | 16 +++++++++++-----
>   1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/librte_lpm/rte_lpm.c b/lib/librte_lpm/rte_lpm.c
> index 2db9e16a2..a6d3a7894 100644
> --- a/lib/librte_lpm/rte_lpm.c
> +++ b/lib/librte_lpm/rte_lpm.c
> @@ -532,11 +532,12 @@ tbl8_alloc(struct rte_lpm *lpm)
>   	return group_idx;
>   }
>   
> -static void
> +static int
>   tbl8_free(struct rte_lpm *lpm, uint32_t tbl8_group_start)
>   {
>   	struct rte_lpm_tbl_entry zero_tbl8_entry = {0};
>   	struct __rte_lpm *internal_lpm;
> +	int rc = 0;
>   
>   	internal_lpm = container_of(lpm, struct __rte_lpm, lpm);
>   	if (internal_lpm->v == NULL) {
> @@ -552,9 +553,13 @@ tbl8_free(struct rte_lpm *lpm, uint32_t tbl8_group_start)
>   				__ATOMIC_RELAXED);
>   	} else if (internal_lpm->rcu_mode == RTE_LPM_QSBR_MODE_DQ) {
>   		/* Push into QSBR defer queue. */
> -		rte_rcu_qsbr_dq_enqueue(internal_lpm->dq,
> +		rc = rte_rcu_qsbr_dq_enqueue(internal_lpm->dq,
>   				(void *)&tbl8_group_start);

On failure rte_rcu_qsbr_dq_enqueue() returns 1 and sets rte_errno. 
Consequently, rc value is propagated to delete_depth_big() -> 
rte_lpm_delete(), and on failure the latter returns "1" value, which 
conflicts with the LPM API:
"0 on success, negative value otherwise"
I would suggest here to return -rte_errno if rc is equal to 1.


> +		if (rc != 0)
> +			RTE_LOG(ERR, LPM, "Failed to push QSBR FIFO\n");
>   	}
> +
> +	return rc;
>   }
>   
>   static __rte_noinline int32_t
> @@ -1041,6 +1046,7 @@ delete_depth_big(struct rte_lpm *lpm, uint32_t ip_masked,
>   	uint32_t tbl24_index, tbl8_group_index, tbl8_group_start, tbl8_index,
>   			tbl8_range, i;
>   	int32_t tbl8_recycle_index;
> +	int rc = 0;
>   
>   	/*
>   	 * Calculate the index into tbl24 and range. Note: All depths larger
> @@ -1097,7 +1103,7 @@ delete_depth_big(struct rte_lpm *lpm, uint32_t ip_masked,
>   		 */
>   		lpm->tbl24[tbl24_index].valid = 0;
>   		__atomic_thread_fence(__ATOMIC_RELEASE);
> -		tbl8_free(lpm, tbl8_group_start);
> +		rc = tbl8_free(lpm, tbl8_group_start);
>   	} else if (tbl8_recycle_index > -1) {
>   		/* Update tbl24 entry. */
>   		struct rte_lpm_tbl_entry new_tbl24_entry = {
> @@ -1113,10 +1119,10 @@ delete_depth_big(struct rte_lpm *lpm, uint32_t ip_masked,
>   		__atomic_store(&lpm->tbl24[tbl24_index], &new_tbl24_entry,
>   				__ATOMIC_RELAXED);
>   		__atomic_thread_fence(__ATOMIC_RELEASE);
> -		tbl8_free(lpm, tbl8_group_start);
> +		rc = tbl8_free(lpm, tbl8_group_start);
>   	}
>   #undef group_idx
> -	return 0;
> +	return (int32_t)rc;
>   }
>   
>   /*
> 

-- 
Regards,
Vladimir