[dm-devel] dm raid: pointer math issue in super_sync()

[Dan Carpenter]

On Tue, Oct 21, 2014 at 08:48:26AM -0400, Mike Snitzer wrote:
> > -	memset(sb + sizeof(*sb), 0, rdev->sb_size - sizeof(*sb));
> > +	memset(sb + 1, 0, rdev->sb_size - sizeof(*sb));
> >  
> >  	sb->magic = cpu_to_le32(DM_RAID_MAGIC);
> >  	sb->features = cpu_to_le32(0);	/* No features yet */
> 
> Not following... sizeof(*sb) != sizeof(sb).  So I'm not seeing a
> problem.
> 
> Nor am I seeing how you think sb + 1 is equivalent to what Heinz
> intended (zero the memory following the sizeof(struct dm_raid_superblock)).

It's pointer math.

sizeof(*sb) is 512.

"sb + sizeof(*sb)" is the same as (void *)sb + 512 * 512.
"sb + 1" is the same as (void *)sb + 512.

regards,
dan carpenter