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Date:   Wed, 15 Feb 2023 12:30:47 -0800
MIME-Version: 1.0
Subject: Re: [PATCH bpf-next 1/7] bpf: Create links for BPF struct_ops maps.
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To:     Kui-Feng Lee <sinquersw@gmail.com>, Kui-Feng Lee <kuifeng@meta.com>
Cc:     bpf@vger.kernel.org, ast@kernel.org, song@kernel.org,
        kernel-team@meta.com, andrii@kernel.org,
        Stanislav Fomichev <sdf@google.com>
References: <20230214221718.503964-1-kuifeng@meta.com>
 <20230214221718.503964-2-kuifeng@meta.com> <Y+xF8k8RMiG0xBDY@google.com>
 <9204de1c-9d98-fe87-77f8-04554210e479@gmail.com>
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From:   Martin KaFai Lau <martin.lau@linux.dev>
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On 2/15/23 10:04 AM, Kui-Feng Lee wrote:
>>> +    int err;
>>> +
>>> +    map = bpf_map_get(attr->link_create.prog_fd);
>>
>> bpf_map_get can fail here?
> 
> 
> We have already verified the `attach_type` of the link before calling this 
> function, so an error should not occur. If it does happen, however, something 
> truly unusual must be happening. To ensure maximum protection and avoid this 
> issue in the future, I will add a check here as well.

bpf_map_get() could fail. A valid attach_type does not mean prog_fd (actually 
map_fd here) is also valid.