Re: [PATCH v5 01/10] crypto: Provide a wrapper function for zeroizing crypto_aes_ctx

[Thomas Huth <thuth@redhat.com>]

On 10/08/2026 11.29, Thomas Huth wrote:
> From: Thomas Huth <thuth@redhat.com>
> 
> Several crypto drivers need to zeroize their local crypto_aes_ctx
> structures after use to avoid leaking key material on the stack.
> Currently some call sites do this with their own memzero_explicit()
> call, which is error-prone since it is easy to miss a return path
> (what already happened in some drivers). Some other call sites miss
> to clear crypto_aes_ctx completely.
> 
> Provide an aes_zeroize_ctx() helper that can be used with __cleanup()
> to automatically zeroize the context when it goes out of scope.
> 
> Acked-by: Eric Biggers <ebiggers@kernel.org>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   include/crypto/aes.h | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/include/crypto/aes.h b/include/crypto/aes.h
> index 3279cfa546085..e70607249ae5c 100644
> --- a/include/crypto/aes.h
> +++ b/include/crypto/aes.h
> @@ -159,6 +159,19 @@ static inline int aes_check_keylen(size_t keylen)
>   int aes_expandkey(struct crypto_aes_ctx *ctx, const u8 *in_key,
>   		  unsigned int key_len);
>   
> +/**
> + * aes_zeroize_ctx - Clear a crypto_aes_ctx structure
> + * @ctx:	The location of the context that should be zeroized
> + *
> + * Explicitly fills the crypto_aes_ctx with zeroes. This should be done
> + * once the context is not required anymore to avoid that its contents
> + * are leaked on the stack or heap (if not using kfree_sensitive()).
> + */
> +static inline void aes_zeroize_ctx(struct crypto_aes_ctx *ctx)
> +{
> +	memzero_explicit(ctx, sizeof(*ctx));
> +}
  Hi Herbert!

Just a quick note: I've included an updated version of this patch in the 
series that targets libcrypto here:

  https://lore.kernel.org/linux-crypto/20260813134953.979481-2-thuth@redhat.com/

... so I think I'll best resubmit the remaining patches of this series here 
once the libcrypto series got accepted.

  Thomas