Re: [dpdk-dev] [PATCH v2] examples/vm_power_manager: fix string null termination

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 26-Apr-19 12:24 PM, David Hunt wrote:
> coverity complains about a null-termination after a read,
> so we terminate after exiting the do-while loop. The position
> is conditional on whether idx is within the buffer or at the
> end of the buffer.
> 
> Coverity issue: 337680
> Fixes: a63504a90f ("examples/power: add JSON string handling")
> CC: stable@dpdk.org
> 
> Signed-off-by: David Hunt <david.hunt@intel.com>
> 
> ---
> v2:
>     * Move null termination outside of do-while.
> ---
>   examples/vm_power_manager/channel_monitor.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/examples/vm_power_manager/channel_monitor.c b/examples/vm_power_manager/channel_monitor.c
> index 971e4f2bc..03fdcd15a 100644
> --- a/examples/vm_power_manager/channel_monitor.c
> +++ b/examples/vm_power_manager/channel_monitor.c
> @@ -822,6 +822,8 @@ read_json_packet(struct channel_info *chan_info)
>   				break;
>   		} while (indent > 0);
>   
> +		json_data[idx + (idx < MAX_JSON_STRING_LEN - 1)] = '\0';
> +

I don't think you need this complicated logic here. You start at idx = 
0, so even if you receive 0 bytes, you'll terminate buffer at index 0. 
You also break when idx reaches (MAX_JSON_STRING_LEN - 1), so it's also 
safe to do json_data[idx] after the loop. In all other cases, you still 
increment idx before breaking out (e.g. when reaching indent == 0), so 
it's also safe to do json_data[idx] in those cases.

>   		if (indent > 0)
>   			/*
>   			 * We've broken out of the read loop without getting
> 


-- 
Thanks,
Anatoly