linux-kernel - [PATCH RFC v2 3/5] KEYS: trusted: Do not use WARN when encode fails

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Date: Sun, 19 May 2024 03:25:38 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: linux-integrity@...r.kernel.org,
	keyrings@...r.kernel.org,
	Andreas.Fuchs@...ineon.com,
	James Prestwood <prestwoj@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	David Howells <dhowells@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Peter Huewe <peterhuewe@....de>,
	Jason Gunthorpe <jgg@...pe.ca>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Stefan Berger <stefanb@...ux.ibm.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Mario Limonciello <mario.limonciello@....com>,
	linux-crypto@...r.kernel.org (open list:CRYPTO API),
	linux-kernel@...r.kernel.org (open list),
	stable@...r.kernel.org,
	Mimi Zohar <zohar@...ux.ibm.com>,
	Paul Moore <paul@...l-moore.com>,
	James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module@...r.kernel.org (open list:SECURITY SUBSYSTEM)
Subject: [PATCH RFC v2 3/5] 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 | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index dfeec06301ce..dbdd6a318b8b 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -38,6 +38,7 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	u8 *end_work = scratch + SCRATCH_SIZE;
 	u8 *priv, *pub;
 	u16 priv_len, pub_len;
+	int ret;
 
 	priv_len = get_unaligned_be16(src) + 2;
 	priv = src;
@@ -79,8 +80,11 @@ 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"))
-		return PTR_ERR(work1);
+	if (IS_ERR(work1)) {
+		ret = PTR_ERR(work1);
+		pr_err("ASN.1 encode error %d\n", ret);
+		return ret;
+	}
 
 	return work1 - payload->blob;
 }
-- 
2.45.1