Re: [PATCH v1] ethdev: fix int overflow in descriptor count logic

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 9/23/24 12:26, Niall Meade wrote:
> Addressed a specific overflow issue in the eth_dev_adjust_nb_desc()
> function where the uint16_t variable nb_desc would overflow when its
> value was greater than (2^16 - nb_align). This overflow caused nb_desc
> to incorrectly wrap around between 0 and nb_align-1, leading to the
> function setting nb_desc to nb_min instead of the expected nb_max.
> 
> The resolution involves upcasting nb_desc to a uint32_t before the
> RTE_ALIGN_CEIL macro is applied. This change ensures that the subsequent
> call to RTE_ALIGN_FLOOR(nb_desc + (nb_align - 1), nb_align) does not
> result in an overflow, as it would when nb_desc is a uint16_t. By using
> a uint32_t for these operations, the correct behavior is maintained
> without the risk of overflow.
> 
> Fixes: 0f67fc3baeb9 ("ethdev: add function to adjust number of descriptors")
> 
> Signed-off-by: Niall Meade <niall.meade@intel.com>

Thanks a lot for the fix.

Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>