Re: FFS: wrong superblock check ~> crash

[Maxime Villard <max%M00nBSD.net@localhost>]

Le 20/10/2014 18:23, David Holland a écrit :
> 
> On Mon, Oct 20, 2014 at 03:38:11PM +0200, Maxime Villard wrote:
>  > I think the sanity check should be:
>  > 
>  > Index: ffs_vfsops.c
>  > ===================================================================
>  > RCS file: /cvsroot/src/sys/ufs/ffs/ffs_vfsops.c,v
>  > retrieving revision 1.299
>  > diff -u -r1.299 ffs_vfsops.c
>  > --- ffs_vfsops.c	24 May 2014 16:34:04 -0000	1.299
>  > +++ ffs_vfsops.c	20 Oct 2014 13:01:46 -0000
>  > @@ -974,7 +974,7 @@
>  >  			continue;
>  >  
>  >  		/* Validate size of superblock */
>  > -		if (sbsize > MAXBSIZE || sbsize < sizeof(struct fs))
>  > +		if (sbsize > SBLOCKSIZE || sbsize < sizeof(struct fs))
>  >  			continue;
>  >  
>  >  		/* Check that we can handle the file system blocksize */
>  > 
>  > Tested on NetBSD-current: no longer crashes.
>  > 
>  > Ok/Comments?
> 
> I think the check should be left alone, but afterwards the value
> should be clamped to the amount of data that can actually be
> transferred. Otherwise I think it may break, e.g. on volumes with odd
> block sizes.

Yes that's what I thought first, but I saw a comment in ffs/fs.h on this:

	"In all cases the size of the superblock will be SBLOCKSIZE."