netdev - Re: [PATCH bpf] xdp: Prevent overflow in devmap_hash cost calculation for 32-bit builds

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Message-ID: <bad3785d-e4d9-82e7-c5ef-f70e44616711@fb.com>
Date:   Fri, 18 Oct 2019 16:44:00 +0000
From:   Yonghong Song <yhs@...com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...com>
CC:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [PATCH bpf] xdp: Prevent overflow in devmap_hash cost calculation
 for 32-bit builds



On 10/17/19 3:57 AM, Toke Høiland-Jørgensen wrote:
> Tetsuo pointed out that without an explicit cast, the cost calculation for
> devmap_hash type maps could overflow on 32-bit builds. This adds the
> missing cast.
> 
> Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
> Reported-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>

Acked-by: Yonghong Song <yhs@...com>

> ---
>   kernel/bpf/devmap.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index a0a1153da5ae..e34fac6022eb 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -128,7 +128,7 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
>   
>   		if (!dtab->n_buckets) /* Overflow check */
>   			return -EINVAL;
> -		cost += sizeof(struct hlist_head) * dtab->n_buckets;
> +		cost += (u64) sizeof(struct hlist_head) * dtab->n_buckets;
>   	}
>   
>   	/* if map size is larger than memlock limit, reject it */
>