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

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Date:	Sun, 15 May 2011 18:29:50 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Alex Davis <alex14641@...oo.com>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: Possible coding issue in udf??

Le dimanche 15 mai 2011 à 08:14 -0700, Andi Kleen a écrit :
> 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);
> >
> > The S_I.. constants are all defined in include/linux/stat.h as 3-bit values.
> >
> > I will send a patch if needed.
> 
> I  would suggest you test it first. Put in a UDF disk that triggers
> this case (verify with a printk). Check in ls -l if the 
> permissions are correct or wrong.

Well, no need to test ;)

Existing code is fine AFAIK.

fs/udf/ecma_167.h

/* Permissions (ECMA 167r3 4/14.9.5) */
#define FE_PERM_O_EXEC                  0x00000001U
#define FE_PERM_O_WRITE                 0x00000002U
#define FE_PERM_O_READ                  0x00000004U

#define FE_PERM_O_CHATTR                0x00000008U
#define FE_PERM_O_DELETE                0x00000010U

#define FE_PERM_G_EXEC                  0x00000020U
#define FE_PERM_G_WRITE                 0x00000040U
#define FE_PERM_G_READ                  0x00000080U

#define FE_PERM_G_CHATTR                0x00000100U
#define FE_PERM_G_DELETE                0x00000200U

#define FE_PERM_U_EXEC                  0x00000400U
#define FE_PERM_U_WRITE                 0x00000800U
#define FE_PERM_U_READ                  0x00001000U
#define FE_PERM_U_CHATTR                0x00002000U
#define FE_PERM_U_DELETE                0x00004000U


So Other bits (inode->i_mode & S_IRWXO) really maps to
FE_PERM_O_EXEC/WRITE/READ

For Group bits (inode->i_mode & S_IRWXG) we must shift by 2 bits to the
left to make them match FE_PERM_G_EXEC/WRITE/READ  (to skip
O_CHATR/O_DELETE)

For Owner/User bits (inode->i_mode & S_IRWXU) we must shift by 4 bits
for same reason.



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