openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 228 insertions, 0 deletions

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
new file mode 100644
index 000000000..1ed686154
--- /dev/null
+++ b/security/integrity/digsig.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2011 Intel Corporation
+ *
+ * Author:
+ * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
+ */
+
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/cred.h>
+#include <linux/kernel_read_file.h>
+#include <linux/key-type.h>
+#include <linux/digsig.h>
+#include <linux/vmalloc.h>
+#include <crypto/public_key.h>
+#include <keys/system_keyring.h>
+
+#include "integrity.h"
+
+static struct key *keyring[INTEGRITY_KEYRING_MAX];
+
+static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
+#ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
+	"_evm",
+	"_ima",
+#else
+	".evm",
+	".ima",
+#endif
+	".platform",
+	".machine",
+};
+
+#ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
+#define restrict_link_to_ima restrict_link_by_digsig_builtin_and_secondary
+#else
+#define restrict_link_to_ima restrict_link_by_digsig_builtin
+#endif
+
+static struct key *integrity_keyring_from_id(const unsigned int id)
+{
+	if (id >= INTEGRITY_KEYRING_MAX)
+		return ERR_PTR(-EINVAL);
+
+	if (!keyring[id]) {
+		keyring[id] =
+			request_key(&key_type_keyring, keyring_name[id], NULL);
+		if (IS_ERR(keyring[id])) {
+			int err = PTR_ERR(keyring[id]);
+			pr_err("no %s keyring: %d\n", keyring_name[id], err);
+			keyring[id] = NULL;
+			return ERR_PTR(err);
+		}
+	}
+
+	return keyring[id];
+}
+
+int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
+			    const char *digest, int digestlen, u8 algo)
+{
+	struct key *keyring;
+
+	if (siglen < 2)
+		return -EINVAL;
+
+	keyring = integrity_keyring_from_id(id);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	switch (sig[1]) {
+	case 1:
+		/* v1 API expect signature without xattr type */
+		return digsig_verify(keyring, sig + 1, siglen - 1, digest,
+				     digestlen);
+	case 2: /* regular file data hash based signature */
+		return asymmetric_verify(keyring, sig, siglen, digest,
+					    digestlen);
+	case 3: /* struct ima_file_id data based signature */
+		return asymmetric_verify_v3(keyring, sig, siglen, digest,
+					    digestlen, algo);
+	}
+
+	return -EOPNOTSUPP;
+}
+
+int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
+{
+	struct key *keyring;
+
+	keyring = integrity_keyring_from_id(id);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	return ima_modsig_verify(keyring, modsig);
+}
+
+static int __init __integrity_init_keyring(const unsigned int id,
+					   key_perm_t perm,
+					   struct key_restriction *restriction)
+{
+	const struct cred *cred = current_cred();
+	int err = 0;
+
+	keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
+				    KGIDT_INIT(0), cred, perm,
+				    KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
+	if (IS_ERR(keyring[id])) {
+		err = PTR_ERR(keyring[id]);
+		pr_info("Can't allocate %s keyring (%d)\n",
+			keyring_name[id], err);
+		keyring[id] = NULL;
+	} else {
+		if (id == INTEGRITY_KEYRING_PLATFORM)
+			set_platform_trusted_keys(keyring[id]);
+		if (id == INTEGRITY_KEYRING_MACHINE && imputed_trust_enabled())
+			set_machine_trusted_keys(keyring[id]);
+		if (id == INTEGRITY_KEYRING_IMA)
+			load_module_cert(keyring[id]);
+	}
+
+	return err;
+}
+
+int __init integrity_init_keyring(const unsigned int id)
+{
+	struct key_restriction *restriction;
+	key_perm_t perm;
+	int ret;
+
+	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
+		| KEY_USR_READ | KEY_USR_SEARCH;
+
+	if (id == INTEGRITY_KEYRING_PLATFORM ||
+	    (id == INTEGRITY_KEYRING_MACHINE &&
+	    !IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) {
+		restriction = NULL;
+		goto out;
+	}
+
+	if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
+		return 0;
+
+	restriction = kzalloc_obj(struct key_restriction);
+	if (!restriction)
+		return -ENOMEM;
+
+	if (id == INTEGRITY_KEYRING_MACHINE)
+		restriction->check = restrict_link_by_ca;
+	else
+		restriction->check = restrict_link_to_ima;
+
+	/*
+	 * MOK keys can only be added through a read-only runtime services
+	 * UEFI variable during boot. No additional keys shall be allowed to
+	 * load into the machine keyring following init from userspace.
+	 */
+	if (id != INTEGRITY_KEYRING_MACHINE)
+		perm |= KEY_USR_WRITE;
+
+out:
+	ret = __integrity_init_keyring(id, perm, restriction);
+	if (ret)
+		kfree(restriction);
+	return ret;
+}
+
+static int __init integrity_add_key(const unsigned int id, const void *data,
+				    off_t size, key_perm_t perm)
+{
+	key_ref_t key;
+	int rc = 0;
+
+	if (!keyring[id])
+		return -EINVAL;
+
+	key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
+				   NULL, data, size, perm,
+				   KEY_ALLOC_NOT_IN_QUOTA);
+	if (IS_ERR(key)) {
+		rc = PTR_ERR(key);
+		if (id != INTEGRITY_KEYRING_MACHINE)
+			pr_err("Problem loading X.509 certificate %d\n", rc);
+	} else {
+		pr_notice("Loaded X.509 cert '%s'\n",
+			  key_ref_to_ptr(key)->description);
+		key_ref_put(key);
+	}
+
+	return rc;
+
+}
+
+int __init integrity_load_x509(const unsigned int id, const char *path)
+{
+	void *data = NULL;
+	size_t size;
+	int rc;
+	key_perm_t perm;
+
+	rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
+					READING_X509_CERTIFICATE);
+	if (rc < 0) {
+		pr_err("Unable to open file: %s (%d)", path, rc);
+		return rc;
+	}
+	size = rc;
+
+	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
+
+	pr_info("Loading X.509 certificate: %s\n", path);
+	rc = integrity_add_key(id, (const void *)data, size, perm);
+
+	vfree(data);
+	return rc;
+}
+
+int __init integrity_load_cert(const unsigned int id, const char *source,
+			       const void *data, size_t len, key_perm_t perm)
+{
+	if (!data)
+		return -EINVAL;
+
+	pr_info("Loading X.509 certificate: %s\n", source);
+	return integrity_add_key(id, data, len, perm);
+}