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References: <20230608072903.3404438-1-lee@kernel.org>
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From:   Eric Dumazet <edumazet@google.com>
Date:   Thu, 8 Jun 2023 09:31:07 +0200
Message-ID: <CANn89iKtkzTKhmeK15BO4uZOBQJhQWgQkaUgT+cxo+BwxE6Ofw@mail.gmail.com>
Subject: Re: [PATCH v2 1/1] net/sched: cls_u32: Fix reference counter leak
 leading to overflow
To:     Lee Jones <lee@kernel.org>
Cc:     jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us,
        davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        stable@kernel.org
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On Thu, Jun 8, 2023 at 9:29=E2=80=AFAM Lee Jones <lee@kernel.org> 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_chang=
e for newly allocated struct")
> Suggested-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Lee Jones <lee@kernel.org>
> ---

Thanks Lee !

Reviewed-by: Eric Dumazet <edumazet@google.com>