linux-kernel - [PATCH v4 1/6] s390/kexec_file: Don't opencode appended signature check.

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Date:   Mon, 10 Jan 2022 14:49:53 +0100
From:   Michal Suchanek <msuchanek@...e.de>
To:     keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-integrity@...r.kernel.org
Cc:     Michal Suchanek <msuchanek@...e.de>, kexec@...ts.infradead.org,
        Philipp Rudo <prudo@...hat.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Nayna <nayna@...ux.vnet.ibm.com>, Rob Herring <robh@...nel.org>,
        linux-s390@...r.kernel.org, Vasily Gorbik <gor@...ux.ibm.com>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Jessica Yu <jeyu@...nel.org>, linux-kernel@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Paul Mackerras <paulus@...ba.org>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org,
        Frank van der Linden <fllinden@...zon.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Daniel Axtens <dja@...ens.net>, buendgen@...ibm.com,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>,
        linux-security-module@...r.kernel.org
Subject: [PATCH v4 1/6] s390/kexec_file: Don't opencode appended signature check.

Module verification already implements appeded signature check.

Reuse it for kexec_file.

The kexec_file implementation uses EKEYREJECTED error in some cases when
there is no key and the common implementation uses ENOPKG or EBADMSG
instead.

Signed-off-by: Michal Suchanek <msuchanek@...e.de>
Acked-by: Heiko Carstens <hca@...ux.ibm.com>
---
v3: Philipp Rudo <prudo@...hat.com>: Update the commit with note about
change of return value
---
 arch/s390/kernel/machine_kexec_file.c | 22 +++++-----------------
 1 file changed, 5 insertions(+), 17 deletions(-)

diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
index 8f43575a4dd3..c944d71316c7 100644
--- a/arch/s390/kernel/machine_kexec_file.c
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -31,6 +31,7 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 	const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
 	struct module_signature *ms;
 	unsigned long sig_len;
+	int ret;
 
 	/* Skip signature verification when not secure IPLed. */
 	if (!ipl_secure_flag)
@@ -45,25 +46,12 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 	kernel_len -= marker_len;
 
 	ms = (void *)kernel + kernel_len - sizeof(*ms);
-	kernel_len -= sizeof(*ms);
+	ret = mod_check_sig(ms, kernel_len, "kexec");
+	if (ret)
+		return ret;
 
 	sig_len = be32_to_cpu(ms->sig_len);
-	if (sig_len >= kernel_len)
-		return -EKEYREJECTED;
-	kernel_len -= sig_len;
-
-	if (ms->id_type != PKEY_ID_PKCS7)
-		return -EKEYREJECTED;
-
-	if (ms->algo != 0 ||
-	    ms->hash != 0 ||
-	    ms->signer_len != 0 ||
-	    ms->key_id_len != 0 ||
-	    ms->__pad[0] != 0 ||
-	    ms->__pad[1] != 0 ||
-	    ms->__pad[2] != 0) {
-		return -EBADMSG;
-	}
+	kernel_len -= sizeof(*ms) + sig_len;
 
 	return verify_pkcs7_signature(kernel, kernel_len,
 				      kernel + kernel_len, sig_len,
-- 
2.31.1