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

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Message-ID: <100542240.i6NpMmsy5C@blindfold>
Date:   Mon, 16 Oct 2017 00:13:43 +0200
From:   Richard Weinberger <richard@....at>
To:     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

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:

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

Thanks,
//richard