Re: [PATCH] smb/server: fix SMB2_MIN_SUPPORTED_HEADER_SIZE value

[ChenXiaoSong <chenxiaosong.chenxiaosong@linux.dev>]

Hi Namjae,

We should rename them to `SMB1_MIN_SUPPORTED_PDU_SIZE` and 
`SMB2_MIN_SUPPORTED_PDU_SIZE`.

But we "should not" add "+4" to them.

The `ksmbd_conn_handler_loop()` function is as follows:

ksmbd_conn_handler_loop()
{
   ...
   pdu_size = get_rfc1002_len(hdr_buf);
   ...
   if (pdu_size < SMB1_MIN_SUPPORTED_HEADER_SIZE)
   ...
   if (pdu_size < SMB2_MIN_SUPPORTED_HEADER_SIZE)
   ...
}

Thanks,
ChenXiaoSong.

On 12/19/25 08:16, Namjae Jeon wrote:
> On Fri, Dec 19, 2025 at 2:11 AM <chenxiaosong.chenxiaosong@linux.dev> wrote:
>>
>> From: ChenXiaoSong <chenxiaosong@kylinos.cn>
>>
>> See RFC1002 4.3.1.
>>
>> The LENGTH field is the number of bytes following the LENGTH
>> field.  In other words, LENGTH is the combined size of the
>> TRAILER field(s).
>>
>> Link: https://lore.kernel.org/linux-cifs/e4fbcbad-459a-412c-918c-0279ec890353@linux.dev/
>> Reported-by: David Howells <dhowells@redhat.com>
>> Signed-off-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
>> ---
>>   fs/smb/server/connection.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/smb/server/connection.c b/fs/smb/server/connection.c
>> index b6b4f1286b9c..da6dfd0d80c2 100644
>> --- a/fs/smb/server/connection.c
>> +++ b/fs/smb/server/connection.c
>> @@ -296,7 +296,7 @@ bool ksmbd_conn_alive(struct ksmbd_conn *conn)
>>   }
>>
>>   #define SMB1_MIN_SUPPORTED_HEADER_SIZE (sizeof(struct smb_hdr))
>> -#define SMB2_MIN_SUPPORTED_HEADER_SIZE (sizeof(struct smb2_hdr) + 4)
>> +#define SMB2_MIN_SUPPORTED_HEADER_SIZE (sizeof(struct smb2_hdr))
> +4 is needed to validate the ByteCount field of the smb1 request and
> the StructureSize2 field of the smb2 request. Let's change the macro
> name from HEADER_SIZE to PDU_SIZE and add +4 to
> SMB1_MIN_SUPPORTED_PDU_SIZE.
>>
>>   /**
>>    * ksmbd_conn_handler_loop() - session thread to listen on new smb requests
>> --
>> 2.43.0
>>