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

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Message-ID: <m2pqnjevjc.fsf@igel.home>
Date:	Sun, 15 May 2011 19:13:59 +0200
From:	Andreas Schwab <schwab@...ux-m68k.org>
To:	Alex Davis <alex14641@...oo.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Possible coding issue in udf??

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
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