From e2861fa71641c6414831d628a1f4f793b6562580 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@google.com>
Date: Fri, 8 Jun 2018 14:57:42 -0700
Subject: evm: Don't deadlock if a crypto algorithm is unavailable

When EVM attempts to appraise a file signed with a crypto algorithm the
kernel doesn't have support for, it will cause the kernel to trigger a
module load. If the EVM policy includes appraisal of kernel modules this
will in turn call back into EVM - since EVM is holding a lock until the
crypto initialisation is complete, this triggers a deadlock. Add a
CRYPTO_NOLOAD flag and skip module loading if it's set, and add that flag
in the EVM case in order to fail gracefully with an error message
instead of deadlocking.

Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 crypto/api.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'crypto')

diff --git a/crypto/api.c b/crypto/api.c
index 0ee632bba064..7aca9f86c5f3 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -229,7 +229,7 @@ static struct crypto_alg *crypto_larval_lookup(const char *name, u32 type,
 	mask &= ~(CRYPTO_ALG_LARVAL | CRYPTO_ALG_DEAD);
 
 	alg = crypto_alg_lookup(name, type, mask);
-	if (!alg) {
+	if (!alg && !(mask & CRYPTO_NOLOAD)) {
 		request_module("crypto-%s", name);
 
 		if (!((type ^ CRYPTO_ALG_NEED_FALLBACK) & mask &
-- 
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