linux-kernel - [PATCH v3] KEYS: prevent NULL pointer dereference in find_asymmetric

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Message-ID: <20240913143010.117883-1-r.smirnov@omp.ru>
Date: Fri, 13 Sep 2024 17:30:09 +0300
From: Roman Smirnov <r.smirnov@....ru>
To: David Howells <dhowells@...hat.com>, Herbert Xu
	<herbert@...dor.apana.org.au>, "David S . Miller" <davem@...emloft.net>,
	Jarkko Sakkinen <jarkko@...nel.org>, Andrew Zaborowski
	<andrew.zaborowski@...el.com>
CC: Roman Smirnov <r.smirnov@....ru>, <keyrings@...r.kernel.org>,
	<linux-crypto@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lvc-project@...uxtesting.org>, Sergey Shtylyov <s.shtylyov@....ru>, Karina
 Yankevich <k.yankevich@....ru>, Sergey Yudin <s.yudin@....ru>
Subject: [PATCH v3] KEYS: prevent NULL pointer dereference in find_asymmetric_key()

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

Add the missing id_2 check and move WARN_ON() to the final else branch
to avoid duplicate NULL checks.

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@....ru>
Signed-off-by: Roman Smirnov <r.smirnov@....ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
---
 V1 -> V2: updated patch description, returned WARN_ON() macro
 V2 -> V3: updated patch description
 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>". */
-- 
2.43.0