linux-kernel - Re: Possible coding issue in udf??

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Message-ID: <177649.65029.qm@web130106.mail.mud.yahoo.com>
Date:	Sun, 15 May 2011 11:04:27 -0700 (PDT)
From:	Alex Davis <alex14641@...oo.com>
To:	Andreas Schwab <schwab@...ux-m68k.org>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Possible coding issue in udf??

I get it now.

Thanks.

I code, therefore I am


--- On Sun, 5/15/11, Andreas Schwab <schwab@...ux-m68k.org> wrote:

> From: Andreas Schwab <schwab@...ux-m68k.org>
> Subject: Re: Possible coding issue in udf??
> To: "Alex Davis" <alex14641@...oo.com>
> Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
> Date: Sunday, May 15, 2011, 1:13 PM
> Alex Davis <alex14641@...oo.com>
> writes:
> 
> > In fs/udf/inode.c, line 1455, linux 2.6.35, there is
> the following code:
> >
> >     udfperms = ((inode->i_mode &
> S_IRWXO)) |
> >        
>    ((inode->i_mode & S_IRWXG) <<
> 2) |
> >        
>    ((inode->i_mode & S_IRWXU) <<
> 4);
> >
> > Shouldn't we be shifting by 3 bits? i.e:
> >     udfperms = ((inode->i_mode &
> S_IRWXO)) |
> >        
>    ((inode->i_mode & S_IRWXG) <<
> 3) |
> >        
>    ((inode->i_mode & S_IRWXU) <<
> 6);
> 
> udfperms contains three bit fields of 5 bits each, of which
> 3 bits are
> each filled from one of the three RWX parts of i_mode, and
> 2 bits
> (DELETE and CHATTR) are added later.  Thus each of the
> three bit fields
> are expanded from 3 to 5 bits, so that the second one needs
> to be
> shifted by 2 and the third one by 4.
> 
> Andreas.
> 
> -- 
> Andreas Schwab, schwab@...ux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3
> 44D5 214B 8276 4ED5
> "And now for something completely different."
> 
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