[PATCH v2] KEYS: prevent NULL pointer dereference in find_asymmetric_key()

[Roman Smirnov]

In find_asymmetric_key(), if all NULLs are passed in id_{0,1,2} parameters
the kernel will first emit WARN and then have an oops because id_2 gets
dereferenced anyway.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: 7d30198ee24f ("keys: X.509 public key issuer lookup without AKID")
Suggested-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
Signed-off-by: Roman Smirnov <r.smirnov@xxxxxx>
Reviewed-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
---
 crypto/asymmetric_keys/asymmetric_type.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c
index a5da8ccd353e..43af5fa510c0 100644
--- a/crypto/asymmetric_keys/asymmetric_type.c
+++ b/crypto/asymmetric_keys/asymmetric_type.c
@@ -60,17 +60,18 @@ struct key *find_asymmetric_key(struct key *keyring,
 	char *req, *p;
 	int len;
 
-	WARN_ON(!id_0 && !id_1 && !id_2);
-
 	if (id_0) {
 		lookup = id_0->data;
 		len = id_0->len;
 	} else if (id_1) {
 		lookup = id_1->data;
 		len = id_1->len;
-	} else {
+	} else if (id_2) {
 		lookup = id_2->data;
 		len = id_2->len;
+	} else {
+		WARN_ON(1);
+		return ERR_PTR(-EINVAL);
 	}
 
 	/* Construct an identifier "id:<keyid>". */
-- 
2.34.1