Re: [patch] UBIFS: use kmalloc_array() in recomp_data_node()

[Dan Carpenter <dan.carpenter@oracle.com>]

On Thu, Nov 22, 2012 at 12:31:37PM +0200, Artem Bityutskiy wrote:
> On Sat, 2012-11-17 at 18:11 +0300, Dan Carpenter wrote:
> >  	out_len = le32_to_cpu(dn->size);
> > -	buf = kmalloc(out_len * WORST_COMPR_FACTOR, GFP_NOFS);
> > +	buf = kmalloc_array(out_len, WORST_COMPR_FACTOR, GFP_NOFS);
> >  	if (!buf)
> >  		return -ENOMEM;
> 
> I think this makes the code unreadable, because we really allocate a
> buffer, not an array.

The problem with the original code is that the multiply looks very
suspect.  Everyone who reads it has to backtrack to find where
dn->size is capped.

I guess in one sense we never allocate an array, we always declare
it on the stack.  We debated the naming and there really isn't a
good name.  kmalloc_safe() isn't right either.  But anyway, the
intent is that eventually someone will right a coccinelle script
which replaces all these allocations with kmalloc_array().

When I look at this code more, I still don't see a place where
dn->size is capped.  So I think we *need* the integer overflow
check as an integer overflow fix and not just as a cleanup.

regards,
dan carpenter