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From:   Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
To:     David Howells <dhowells@redhat.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Gilad Ben-Yossef <gilad@benyossef.com>,
        Tobias Markus <tobias@markus-regensburg.de>,
        Tee Hao Wei <angelsl@in04.sg>, keyrings@vger.kernel.org,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Cc:     Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Subject: [PATCH] X.509: Fix crash caused by NULL pointer
Date:   Thu,  7 Jan 2021 17:28:55 +0800
Message-Id: <20210107092855.76093-1-tianjia.zhang@linux.alibaba.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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")
Cc: stable@vger.kernel.org # v5.10+
Reported-by: Tobias Markus <tobias@markus-regensburg.de>
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
---
 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;
-- 
2.19.1.3.ge56e4f7