[linux-cifs-client] [PATCH] cifs: Fix insufficient memory allocation for nativeFileSystem field

[simo]

On Mon, 2009-04-06 at 09:22 -0400, Jeff Layton wrote:
> > True. Seems I was influenced by a comment in fs/cifs/sess.c
> > 
> > 313         /* UTF-8 string will not grow more than four times as
> big as
> > UCS-16 */
> > 
> 
> That looks like that's wrong (or at least potentially so). AFAICT,
> UTF-8
> allows up to 6 bytes per character. I suppose that it's possible that
> none of the characters allowed in UCS-16 will ever translate to a
> character that's more than 4 bytes, but I'd like to see that confirmed
> before we depend on it.

I wonder whats UCS-16 tho, UCS-16 does not exist :)

It may be either UTF16 or UCS2.
Both these charsets have a base length of 2 bytes per character. UCS2 is
limited to 65535 values, while UTF-16 is a multi-word charset.

If the comment above is to be read as "UTF-8 string will not grow more
than four times as big as UCS-2/UTF-16" then what it is saying is that
at maximum an UTF-8 chars can be 4 words (or 8 bytes long).
IIRC UTF-8 chars length is maximum 6 bytes, so an 8 byte per char max
estimate seem correct.

If "length" in the code was the length in bytes, and not the number of
characters, of an UCS-2/UTF-16 string than 4*length should, indeed be
long enough.

Simo. 

-- 
Simo Sorce
Samba Team GPL Compliance Officer <simo at samba.org>
Principal Software Engineer at Red Hat, Inc. <simo at redhat.com>