netdev - Re: [PATCH] bpf: fix kmalloc bug in bpf

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Message-ID: <4f260295-b7a2-92ad-3bb0-06074288dd23@fb.com>
Date:   Mon, 13 Sep 2021 08:33:51 -0700
From:   Yonghong Song <yhs@...com>
To:     Dongliang Mu <mudongliangabcd@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Willy Tarreau <w@....eu>
CC:     <syzbot+f3e749d4c662818ae439@...kaller.appspotmail.com>,
        <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: fix kmalloc bug in bpf_check



On 9/13/21 4:02 AM, Dongliang Mu wrote:
> Since 7661809d493b ("mm: don't allow oversized kvmalloc() calls
> ") does not allow oversized kvmalloc, it triggers a kmalloc bug warning
> at bpf_check.
> 
> Fix it by adding a sanity check in th check_btf_line.
> 
> Reported-by: syzbot+f3e749d4c662818ae439@...kaller.appspotmail.com
> Fixes: 7661809d493b ("mm: don't allow oversized kvmalloc() calls")
> Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>

Thanks for the fix. A similar patch has been proposed here:
https://lore.kernel.org/bpf/20210911005557.45518-1-cuibixuan@huawei.com/

> ---
>   kernel/bpf/verifier.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 047ac4b4703b..3c5a79f78bc5 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -9913,6 +9913,9 @@ static int check_btf_line(struct bpf_verifier_env *env,
>   	if (!nr_linfo)
>   		return 0;
>   
> +	if (nr_linfo > INT_MAX/sizeof(struct bpf_line_info))
> +		return -EINVAL;
> +
>   	rec_size = attr->line_info_rec_size;
>   	if (rec_size < MIN_BPF_LINEINFO_SIZE ||
>   	    rec_size > MAX_LINEINFO_REC_SIZE ||
>