linux-kernel - Re: [PATCH] ksmbd: validate the zero field of packet header

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Date:   Fri, 8 Dec 2023 10:34:46 -0500
From:   Tom Talpey <tom@...pey.com>
To:     Namjae Jeon <linkinjeon@...nel.org>, linan666@...weicloud.com
Cc:     sfrench@...ba.org, linux-cifs@...r.kernel.org,
        linux-kernel@...r.kernel.org, linan122@...wei.com,
        yukuai3@...wei.com, yi.zhang@...wei.com, houtao1@...wei.com,
        yangerkun@...wei.com
Subject: Re: [PATCH] ksmbd: validate the zero field of packet header

On 12/8/2023 9:20 AM, Namjae Jeon wrote:
> 2023-12-08 15:56 GMT+09:00, linan666@...weicloud.com <linan666@...weicloud.com>:
>> From: Li Nan <linan122@...wei.com>
>>
>> The SMB2 Protocol requires that "The first byte of the Direct TCP
>> transport packet header MUST be zero (0x00)"[1]. Commit 1c1bcf2d3ea0
>> ("ksmbd: validate smb request protocol id") removed the validation of
>> this 1-byte zero. Add the validation back now.
>>
>> [1]: [MS-SMB2] - v20230227, page 30.
>> https://winprotocoldoc.blob.core.windows.net/productionwindowsarchives/MS-SMB2/%5bMS-SMB2%5d-230227.pdf
>>
>> Fixes: 1c1bcf2d3ea0 ("ksmbd: validate smb request protocol id")
>> Signed-off-by: Li Nan <linan122@...wei.com>
> Acked-by: Namjae Jeon <linkinjeon@...nel.org>
> Applied it to #ksmbd-for-next-next.
> Thanks for your patch!
> 
> 

Technically speaking, the first byte of the 4-byte header is a flag
used for multi-segment continuation/reassembly. But since ksmbd does
not have any code to do such processing, it's best to deny the
message. So...

Acked-by: Tom Talpey <tom@...pey.com>