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    SubjectRe: [PATCH RFC v2] slab: introduce kmalloc_array
    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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