Re: [PATCH v2] crypto: arm64/aes-neonbs - Move key expansion off the stack

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Mar 06, 2026 at 02:42:54PM +0800, Cheng-Yang Chou wrote:
> aesbs_setkey() and aesbs_cbc_ctr_setkey() allocate struct crypto_aes_ctx
> on the stack. On arm64, the kernel-mode NEON context is also stored on
> the stack, causing the combined frame size to exceed 1024 bytes and
> triggering -Wframe-larger-than= warnings.
> 
> Allocate struct crypto_aes_ctx on the heap instead and use
> kfree_sensitive() to ensure the key material is zeroed on free.
> Use a goto-based cleanup path to ensure kfree_sensitive() is always
> called.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
> Changes in v1:
> - Replace memzero_explicit() + kfree() with kfree_sensitive()
>   (Eric Biggers)
> - Link to v1: https://lore.kernel.org/all/20260305183229.150599-1-yphbchou0911@gmail.com/
> 
>  arch/arm64/crypto/aes-neonbs-glue.c | 37 ++++++++++++++++++-----------
>  1 file changed, 23 insertions(+), 14 deletions(-)

Looks okay for now, though as I mentioned I'd like to eventually
refactor this code to not need so much temporary space.

I'll plan to take this through the libcrypto-fixes tree.  Herbert, let
me know if you prefer to take it instead.

I'll plan to add:

    Fixes: 4fa617cc6851 ("arm64/fpsimd: Allocate kernel mode FP/SIMD buffers on the stack")

... since that is the change that put the stack usage over the "limit".

- Eric