Re: cramfs mounts provide corrupted content since 2.6.15

[Dave Johnson <djohnson+linux-kernel@sw.starentnetworks.com>]

Chris Mason writes:
> On Monday 27 February 2006 11:31, Dave Johnson wrote:
> 
> > I think I've spotted an issue.
> >
> > Both ifind() and find_inode() will call the test function on inodes
> > that still have I_LOCK|I_NEW set.  This means everything that the
> > test function needs _must_ be set in the set function (which is called
> > while the inode_lock is still held).
> >
> > This could cause issues for inodes of 1 (only i_ino is getting set
> > right now).
> 
> The problem is that two files are getting the same inode number because 
> their offsets are the same.
> 
> ls -lai:
> 3412140 -rw-r--r--  1 root root       0 Jan  1  1970 ./etc/mtab
> 3412140 -rw-r--r--  1 root root    1220 Jan  1  1970 ./etc/nsswitch.conf
> 
> So, if /etc/mtab is read first, /etc/nsswitch.conf ends up with size zero, 
> because it uses the mtab inode.
> 
> Andreas Gruenbacher suggested this change.  Along with your patch, things 
> are working here again:
> 
> -chris
> 
> diff -r 0f4fc87886c2 fs/cramfs/inode.c
> --- a/fs/cramfs/inode.c	Fri Feb 24 16:18:23 2006 -0500
> +++ b/fs/cramfs/inode.c	Tue Feb 28 14:00:11 2006 -0500
> @@ -36,7 +36,7 @@ static DECLARE_MUTEX(read_mutex);
>  
>  /* These two macros may change in future, to provide better st_ino
>     semantics. */
> -#define CRAMINO(x)	((x)->offset?(x)->offset<<2:1)
> +#define CRAMINO(x)	(((x)->offset && (x)->size)?(x)->offset<<2:1)
>  #define OFFSET(x)	((x)->i_ino)


What version of mkcramfs are you using?  Empty regular files should
have offset set to 0 already.


-- 
Dave Johnson
Starent Networks