linux-kernel - [PATCH 3/3] KEYS: trusted: Do not use WARN when encode fails

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Date: Mon, 20 May 2024 02:51:21 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: linux-integrity@...r.kernel.org
Cc: keyrings@...r.kernel.org,
	James.Bottomley@...senPartnership.com,
	Jarkko Sakkinen <jarkko@...nel.org>,
	stable@...r.kernel.org,
	Mimi Zohar <zohar@...ux.ibm.com>,
	David Howells <dhowells@...hat.com>,
	Paul Moore <paul@...l-moore.com>,
	James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] KEYS: trusted: Do not use WARN when encode fails

When asn1_encode_sequence() fails, WARN is not the correct solution.

1. asn1_encode_sequence() is not an internal function (located
   in lib/asn1_encode.c).
2. Location is known, which makes the stack trace useless.
3. Results a crash if panic_on_warn is set.

It is also noteworthy that the use of WARN is undocumented, and it
should be avoided unless there is a carefully considered rationale to
use it.

Replace WARN with pr_err, and print the return value instead, which is
only useful piece of information.

Cc: stable@...r.kernel.org # v5.13+
Fixes: f2219745250f ("security: keys: trusted: use ASN.1 TPM2 key format for the blobs")
Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
---
 security/keys/trusted-keys/trusted_tpm2.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index c6882f5d094f..8b7dd73d94c1 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -84,8 +84,9 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	work1 = payload->blob;
 	work1 = asn1_encode_sequence(work1, work1 + sizeof(payload->blob),
 				     scratch, work - scratch);
-	if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed")) {
+	if (IS_ERR(work1)) {
 		ret = PTR_ERR(work1);
+		pr_err("BUG: ASN.1 encoder failed with %d\n", ret);
 		goto err;
 	}
 
-- 
2.45.1