linux-kernel - [PATCH] X.509: Fix crash caused by NULL pointer

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Date:   Tue, 19 Jan 2021 00:13:19 +0000
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org
Cc:     Tobias Markus <tobias@...kus-regensburg.de>,
        Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>,
        dhowells@...hat.com, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org,
        linux-security-module@...r.kernel.org, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] X.509: Fix crash caused by NULL pointer


From: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>

On the following call path, `sig->pkey_algo` is not assigned
in asymmetric_key_verify_signature(), which causes runtime
crash in public_key_verify_signature().

  keyctl_pkey_verify
    asymmetric_key_verify_signature
      verify_signature
        public_key_verify_signature

This patch simply check this situation and fixes the crash
caused by NULL pointer.

Fixes: 215525639631 ("X.509: support OSCCA SM2-with-SM3 certificate verification")
Reported-by: Tobias Markus <tobias@...kus-regensburg.de>
Signed-off-by: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Reviewed-and-tested-by: Toke Høiland-Jørgensen <toke@...hat.com>
Tested-by: João Fonseca <jpedrofonseca@...pt>
Cc: stable@...r.kernel.org # v5.10+
---

 crypto/asymmetric_keys/public_key.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index 8892908ad58c..788a4ba1e2e7 100644
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -356,7 +356,8 @@ int public_key_verify_signature(const struct public_key *pkey,
 	if (ret)
 		goto error_free_key;
 
-	if (strcmp(sig->pkey_algo, "sm2") == 0 && sig->data_size) {
+	if (sig->pkey_algo && strcmp(sig->pkey_algo, "sm2") == 0 &&
+	    sig->data_size) {
 		ret = cert_sig_digest_update(sig, tfm);
 		if (ret)
 			goto error_free_key;