[PATCH v3 3/7] 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 <ardb at kernel.org>
---
 crypto/skcipher.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 93fdacf49697..9bce5350008b 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -625,6 +625,11 @@ 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;
@@ -642,6 +647,11 @@ 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;
-- 
2.20.1