Messages in this thread | | | Date | Mon, 13 Feb 2012 14:27:55 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH RFC v2] slab: introduce kmalloc_array |
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On Mon, 13 Feb 2012, Dan Carpenter wrote:
> > The point was that there are a bunch of places where we have had > integer overflows caused by doing kmalloc(x * sizeof(struct whatever)). > For kzalloc(x * sizeof(struct whatever)), you just write it like > kcalloc(x, sizeof(struct whatever)) and avoid the overflow, but we > don't have a non-zeroing version of kcalloc() to do that. > > Probably once we have the kmalloc_array() and people start using it, > we get a bunch of overflow checking automatically and it's a kernel > hardenning thing. As well we could remove the duplicative checking > so it's a cleanup.
Could you just do a macro that can be used in any location where the size of an array needs to be calculation. For example:
SAFE_ARRAY_SIZE(<nr>,<struct>)
So you'd do
kmalloc_node(SAFE_ARRAY_SIZE(10, struct page), 2, GFP_KERNEL)
or if you want multiple dimensions
SAFE_ARRAY_SIZE_2(<nr1>,<nr2>,<struct>)
?
> > If you add these variants then please think > > about the necessity to add other variants (like the kmalloc_node() NUMA > > call) etc in the future. > > > > We don't have a kcalloc_node(), so I don't think this is likely to > be a big issue.
Yes and so if you need to allocate on a particular node then you need to do the calculation manually and therefore may not check for overflows.
Get rid of kcalloc and replace it with
kzalloc(SAFE_ARRAY_SIZE(x, y), ....)
?
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