[RFC PATCH 2/5] crypto: skcipher - disallow en/decrypt for non-task or non-softirq context

[Ard Biesheuvel]

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
skcipher encrypt and decrypt routines from outside of task or softirq
context.

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

diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index b4dae640de9f..d1a656d7d498 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -628,6 +628,11 @@ int crypto_skcipher_encrypt(struct skcipher_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_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
                ret = -ENOKEY;
@@ -645,6 +650,11 @@ int crypto_skcipher_decrypt(struct skcipher_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_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
                ret = -ENOKEY;
-- 
2.17.1