netdev - Re: [PATCH] bpf: devmap: Check attr->max

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Message-ID: <0b5e4a49-3738-5b57-1abf-1912b2afff2c@gmail.com>
Date:   Mon, 16 Oct 2017 21:30:38 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Richard Weinberger <richard@....at>, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, daniel@...earbox.net, ast@...nel.org,
        sp3485@...umbia.edu
Subject: Re: [PATCH] bpf: devmap: Check attr->max_entries more carefully

On 10/15/2017 03:13 PM, Richard Weinberger wrote:
> Am Montag, 16. Oktober 2017, 00:00:20 CEST schrieb Richard Weinberger:
>> max_entries is user controlled and used as input for __alloc_percpu().
>> This function expects that the allocation size is a power of two and
>> less than PCPU_MIN_UNIT_SIZE.
>> Otherwise a WARN() is triggered.
> 
> On a second though, I think we should also have a hard limit for ->max_entries 
> or check for an overflow here:
> 

Or just,

static u64 dev_map_bitmap_size(const union bpf_attr *attr)
{
	return BITS_TO_LONGS((u64) attr->max_entries) *
		sizeof(unsigned long);
}

Let me know if you want me to send a patch or if you want to.

Thanks,
John

> static u64 dev_map_bitmap_size(const union bpf_attr *attr)
> {
>         return BITS_TO_LONGS(attr->max_entries) * sizeof(unsigned long);
> }
> 
> Thanks,
> //richard
>