linux-kernel - [PATCH 5.10 06/43] X.509: Fix crash caused by NULL pointer

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Message-Id: <20210122135735.910313266@linuxfoundation.org>
Date:   Fri, 22 Jan 2021 15:12:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Tobias Markus <tobias@...kus-regensburg.de>,
        Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>,
        David Howells <dhowells@...hat.com>,
        João Fonseca <jpedrofonseca@...pt>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: [PATCH 5.10 06/43] X.509: Fix crash caused by NULL pointer

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

commit 7178a107f5ea7bdb1cc23073234f0ded0ef90ec7 upstream.

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>
Acked-by: Jarkko Sakkinen <jarkko@...nel.org>
Cc: stable@...r.kernel.org # v5.10+
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -356,7 +356,8 @@ int public_key_verify_signature(const st
 	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;