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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <20210112161044.3101-1-toke@redhat.com>
References: <20210112161044.3101-1-toke@redhat.com>
To:     =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Cc:     dhowells@redhat.com, Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
        Gilad Ben-Yossef <gilad@benyossef.com>,
        keyrings@vger.kernel.org, linux-crypto@vger.kernel.org,
        stable@vger.kernel.org
Subject: Re: [PATCH] crypto: public_key: check that pkey_algo is non-NULL before passing it to strcmp()
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Content-ID: <2648794.1610536273.1@warthog.procyon.org.uk>
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Date:   Wed, 13 Jan 2021 11:11:13 +0000
Message-ID: <2648795.1610536273@warthog.procyon.org.uk>
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I'm intending to use Tianjia's patch.  Would you like to add a Reviewed-by=
?

David
---
commit 11078a592e6dcea6b9f30e822d3d30e3defc99ca
Author: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Date:   Thu Jan 7 17:28:55 2021 +0800

    X.509: Fix crash caused by NULL pointer
    =

    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 ve=
rification")
    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>
    Signed-off-by: David Howells <dhowells@redhat.com>

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_ke=
y *pkey,
 	if (ret)
 		goto error_free_key;
 =

-	if (strcmp(sig->pkey_algo, "sm2") =3D=3D 0 && sig->data_size) {
+	if (sig->pkey_algo && strcmp(sig->pkey_algo, "sm2") =3D=3D 0 &&
+	    sig->data_size) {
 		ret =3D cert_sig_digest_update(sig, tfm);
 		if (ret)
 			goto error_free_key;