Re: [PATCH v2 1/1] net/sched: cls_u32: Fix reference counter leak leading to overflow

[Eric Dumazet]

On Thu, Jun 8, 2023 at 9:29 AM Lee Jones <lee@xxxxxxxxxx> wrote:
>
> In the event of a failure in tcf_change_indev(), u32_set_parms() will
> immediately return without decrementing the recently incremented
> reference counter.  If this happens enough times, the counter will
> rollover and the reference freed, leading to a double free which can be
> used to do 'bad things'.
>
> In order to prevent this, move the point of possible failure above the
> point where the reference counter is incremented.  Also save any
> meaningful return values to be applied to the return data at the
> appropriate point in time.
>
> This issue was caught with KASAN.
>
> Fixes: 705c7091262d ("net: sched: cls_u32: no need to call tcf_exts_change for newly allocated struct")
> Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
> ---

Thanks Lee !

Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>