On So, 2014-09-07 at 23:23 +0200, Daniel Borkmann wrote:
> Recently, in commit 13aa93c70e71 ("random: add and use memzero_explicit()
> for clearing data"), we have found that GCC may optimize some memset()
> cases away when it detects a stack variable is not being used anymore
> and going out of scope. This can happen, for example, in cases when we
> are clearing out sensitive information such as keying material or any
> e.g. intermediate results from crypto computations, etc.
>
> With the help of Coccinelle, we can figure out and fix such occurences
> in the crypto subsytem as well. Julia Lawall provided the following
> Coccinelle program:
>
> @@
> type T;
> identifier x;
> @@
>
> T x;
> ... when exists
> when any
> -memset
> +memzero_explicit
> (&x,
> -0,
> ...)
> ... when != x
> when strict
>
> @@
> type T;
> identifier x;
> @@
>
> T x[...];
> ... when exists
> when any
> -memset
> +memzero_explicit
> (x,
> -0,
> ...)
> ... when != x
> when strict
I think this Coccinelle patch won't make it completely unnecessary for a
manual audit as it does not take optimizations (dead code eliminitation)
into account?
>
> Therefore, make use of the drop-in replacement memzero_explicit() for
> exactly such cases instead of using memset().
>
> Signed-off-by: Daniel Borkmann <[email protected]>
> Cc: Julia Lawall <[email protected]>
> Cc: Herbert Xu <[email protected]>
> Cc: Theodore Ts'o <[email protected]>
> Cc: Hannes Frederic Sowa <[email protected]>
Acked-by: Hannes Frederic Sowa <[email protected]
Thanks,
Hannes
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