Re: [PATCH v5 01/10] crypto: Provide a wrapper function for zeroizing crypto_aes_ctx
From: Thomas Huth
Date: Thu Aug 13 2026 - 10:17:27 EST
On 10/08/2026 11.29, Thomas Huth wrote:
From: Thomas Huth <thuth@xxxxxxxxxx>Hi Herbert!
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@xxxxxxxxxx>
Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
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));
+}
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@xxxxxxxxxx/
... so I think I'll best resubmit the remaining patches of this series here once the libcrypto series got accepted.
Thomas