On Wed, 12 May 2021 at 22:06, Eric Biggers [off-list ref] wrote:

On Wed, May 12, 2021 at 08:44:34PM +0200, Ard Biesheuvel wrote:

quoted

In order to ensure that kernel mode SIMD routines will not need a scalar
fallback if they run with softirqs disabled, disallow any use of the
AEAD encrypt and decrypt routines from outside of task or softirq context.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 crypto/aead.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/crypto/aead.c b/crypto/aead.c
index 16991095270d..b5304b3d3314 100644
--- a/crypto/aead.c
+++ b/crypto/aead.c

@@ -87,6 +87,11 @@ int crypto_aead_encrypt(struct aead_request *req)
      unsigned int cryptlen = req->cryptlen;
      int ret;

+     if (!(alg->cra_flags & CRYPTO_ALG_ASYNC) &&
+         WARN_ONCE(!in_task() && !in_serving_softirq(),
+                   "synchronous call from invalid context\n"))
+             return -EBUSY;
+
      crypto_stats_get(alg);
      if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
              ret = -ENOKEY;

@@ -104,6 +109,11 @@ int crypto_aead_decrypt(struct aead_request *req)
      unsigned int cryptlen = req->cryptlen;
      int ret;

+     if (!(alg->cra_flags & CRYPTO_ALG_ASYNC) &&
+         WARN_ONCE(!in_task() && !in_serving_softirq(),
+                   "synchronous call from invalid context\n"))
+             return -EBUSY;
+
      crypto_stats_get(alg);
      if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
              ret = -ENOKEY;

This probably should go after crypto_stats_get() so that the error gets counted
in the stats (if stats are enabled) -- analogous to how the ENOKEY error is
counted.

Likewise for the skcipher patch.

Good point, I'll fix that