From: Miloslav Trmac <mitr-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: crypto apis in cifs module allocating storage for character
 array during run-time vs. dynamic allocation
Date: Mon, 23 Aug 2010 18:39:17 -0400 (EDT)
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----- "Shirish Pargaonkar" <shirishpargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Instead of determining and allocating a char array for use during usage of
> crypto_shash_* calls, would like to instead dynamically
> allocate (and free) storage for the duration of crypto calculation
> (crypto_shash_init,
> crypto_shash_update, and crypto_shash_final)
> But everytime I try, it results in some sort of oops in the cifs module.
Let me just suggest something, without trying it...

> +struct sdesc {
> +       struct shash_desc shash;
> +       char *ctx;
        char ctx[];
would be correct here.
> +};
And you need to allocate both shash_desc and "ctx" together as a single piece of memory - exactly mirror the memory layout of the original "sdesc" variable.
    Mirek