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

[Tom Talpey]

On 12/8/2023 9:20 AM, Namjae Jeon wrote:
> 2023-12-08 15:56 GMT+09:00, linan666@xxxxxxxxxxxxxxx <linan666@xxxxxxxxxxxxxxx>:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> Acked-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
> 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@xxxxxxxxxx>