[PATCH 4.8 025/138] security/keys: make BIG_KEYS dependent on stdrng.

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Artem Savkov <asavkov@xxxxxxxxxx>

commit 31e6ec4519c0fe0ee4a2f6ba3ab278e9506b9500 upstream.

Since BIG_KEYS can't be compiled as module it requires one of the "stdrng"
providers to be compiled into kernel. Otherwise big_key_crypto_init() fails
on crypto_alloc_rng step and next dereference of big_key_skcipher (e.g. in
big_key_preparse()) results in a NULL pointer dereference.

Fixes: 13100a72f40f5748a04017e0ab3df4cf27c809ef ('Security: Keys: Big keys stored encrypted')
Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Stephan Mueller <smueller@xxxxxxxxxx>
cc: Kirill Marinushkin <k.marinushkin@xxxxxxxxx>
Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 security/keys/Kconfig |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -41,7 +41,7 @@ config BIG_KEYS
 	bool "Large payload keys"
 	depends on KEYS
 	depends on TMPFS
-	select CRYPTO
+	depends on (CRYPTO_ANSI_CPRNG = y || CRYPTO_DRBG = y)
 	select CRYPTO_AES
 	select CRYPTO_ECB
 	select CRYPTO_RNG