Re: [dpdk-dev] [PATCH] examples/exception_path: fix shift operation in lcore setup

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

On 8/3/2016 12:44 PM, Daniel Mrzyglod wrote:
> The operaton may have an undefined behavior or yield to an unexpected result.
> A bit shift operation has a shift amount which is too large or has a negative value.
> 
> Coverity issue: 30688
> Fixes: ea977ff1cb0b ("examples/exception_path: fix shift operation in lcore setup")
> The previous patch forget to fix values also for input_cores_mask
> 
> Signed-off-by: Daniel Mrzyglod <danielx.t.mrzyglod@intel.com>
> ---
>  examples/exception_path/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/examples/exception_path/main.c b/examples/exception_path/main.c
> index e5eedcc..88e7708 100644
> --- a/examples/exception_path/main.c
> +++ b/examples/exception_path/main.c
> @@ -341,7 +341,7 @@ setup_port_lcore_affinities(void)
>  
>  	/* Setup port_ids[] array, and check masks were ok */
>  	RTE_LCORE_FOREACH(i) {
> -		if (input_cores_mask & (1ULL << i)) {
> +		if (input_cores_mask & (1ULL << (i & 0x3f))) {

I guess 0x3f is because "unsigned long long" is 64bits long, not sure if
we should hardcode this assumption. ULL can be >= 64bits.

RTE_LCORE_FOREACH(i) already makes sure "i" < RTE_MAX_CORE, and
RTE_MAX_CORE is 128 with current default config. So if user provides a
core value > 64, it is valid but will be ignored because of this check.

Another thing is "input_cores_mask" is also 64bits long, so even this
fixed application will not able to use this setting correctly.

I think it is good to
a) add flexible variable size set_bit/clear_bit/test_bit functions, like
Linux ones
b) make "input_cores_mask" an array that is large enough to keep
RTE_MAX_CORE

Although not sure if that is too much effort for this fix.

>  			/* Skip ports that are not enabled */
>  			while ((ports_mask & (1 << rx_port)) == 0) {
>  				rx_port++;
>