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SubjectRe: on stack dynamic allocations
On 08/16/2012 02:20 PM, Kasatkin, Dmitry wrote:
> Hello,
>
> Some places in the code uses variable-size allocation on stack..
> For example from hmac_setkey():
>
> struct {
> struct shash_desc shash;
> char ctx[crypto_shash_descsize(hash)];
> } desc;
>
>
> sparse complains
>
> CHECK crypto/hmac.c
> crypto/hmac.c:57:47: error: bad constant expression
>
> I like it instead of kmalloc..
>
> But what is position of kernel community about it?

If you know that the range of crypto_shash_descsize(hash) is bounded,
just use the upper bound.

If the range of crypto_shash_descsize(hash) is unbounded, then the stack
will overflow and ... BOOM!

David Daney





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