[linux-cifs-client] Null-Terminating bcc_ptr wrong?

[Christopher R. Hertel]

Peter Hudec wrote:
> Christopher R. Hertel wrote:
>> This is a tangent, but...
>>
>> It shouldn't be UTF-8.  CIFS (the protocol) supports UCS-16LE Unicode
>> encoding or 8-bit extended ASCII (OEM charset).
>>
>> Chris -)-----
> The protocol SMB/CIFS uses UCS-2LE (to be correct), but the conversion
> may be done to UTF-8.

So, I double checked.  :)

You are correct that there is no "UCS-16LE".  Ooops.  What I meant to write
was UTF-16LE.  According to current docs ([MS-UCODEREF]), Microsoft supports
full UTF-16 as opposed to UCS-2.

> The UCS-2LE-string from the packet can grow up to 4 bytes/character or
> twice as big as UCS-2LE (it can - it does not necessarily do so!)

UCS-2 does not support surrogate pairs, so the encoding is actually fixed at
16 bits per code point.  UTF-16 does support surrogate pairs, which is where
the expansion becomes possible.

> To determine the size of the target buffer without calculating it the
> correct line should be:
> 
> tcon->nativeFileSystem = kzalloc(4 * (length + 1), GFP_KERNEL);

That'd be the safe way, though the terminating nul would still be only 2
bytes so you could subtract two from the total.  ((4 * (length + 1)) - 2)

> tcon->nativeFileSystem is a buffer in the specific codepage. If it is
> ISO 5598-1, e.g., it is fine, because it needs 8 bit (1 byte) per
> character. If it is UTF-8, and only consists of ASCII (like "NTFS",
> "FAT32"), it is fine too and only needs one byte per character.
> But in a worse case (is there any file system containing special
> characters? I don't know any) the buffer can grow up to 4 bytes per
> character.

I know of one proposed file system that has a name that would require
Unicode (and probably four-byte encoding).  It's only a dream at this point,
however, so it's not relevant.

Fun.

Chris -)-----

-- 
"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team -- http://www.samba.org/     -)-----   Christopher R. Hertel
jCIFS Team -- http://jcifs.samba.org/   -)-----   ubiqx development, uninq.
ubiqx Team -- http://www.ubiqx.org/     -)-----   crh at ubiqx.mn.org
OnLineBook -- http://ubiqx.org/cifs/    -)-----   crh at ubiqx.org