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From:   Ard Biesheuvel <ardb@kernel.org>
To:     linux-crypto@vger.kernel.org
Cc:     linux-arm-kernel@lists.infradead.org, ebiggers@kernel.org,
        herbert@gondor.apana.org.au, will@kernel.org,
        kernel-team@android.com, Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH v4 2/7] crypto: aead - disallow en/decrypt for non-task or non-softirq context
Date:   Wed, 19 May 2021 13:22:34 +0200
Message-Id: <20210519112239.33664-3-ardb@kernel.org>
In-Reply-To: <20210519112239.33664-1-ardb@kernel.org>
References: <20210519112239.33664-1-ardb@kernel.org>
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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 | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/crypto/aead.c b/crypto/aead.c
index 16991095270d..141c9369b02a 100644
--- a/crypto/aead.c
+++ b/crypto/aead.c
@@ -88,7 +88,11 @@ int crypto_aead_encrypt(struct aead_request *req)
 	int ret;
 
 	crypto_stats_get(alg);
-	if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
+	if (!(alg->cra_flags & CRYPTO_ALG_ASYNC) &&
+	    WARN_ONCE(!in_task() && !in_serving_softirq(),
+		      "synchronous call from invalid context\n"))
+		ret = -EBUSY;
+	else if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
 		ret = -ENOKEY;
 	else
 		ret = crypto_aead_alg(aead)->encrypt(req);
@@ -105,7 +109,11 @@ int crypto_aead_decrypt(struct aead_request *req)
 	int ret;
 
 	crypto_stats_get(alg);
-	if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
+	if (!(alg->cra_flags & CRYPTO_ALG_ASYNC) &&
+	    WARN_ONCE(!in_task() && !in_serving_softirq(),
+		      "synchronous call from invalid context\n"))
+		ret = -EBUSY;
+	else if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
 		ret = -ENOKEY;
 	else if (req->cryptlen < crypto_aead_authsize(aead))
 		ret = -EINVAL;
-- 
2.20.1