linux-kernel - [PATCH, RFC 37/62] keys/mktme: Do not allow key creation in unsafe topologies

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Date:   Wed,  8 May 2019 17:43:57 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH, RFC 37/62] keys/mktme: Do not allow key creation in unsafe topologies

From: Alison Schofield <alison.schofield@...el.com>

MKTME feature depends upon at least one online CPU capable of
programming each memory controller in the platform.

An unsafe topology for MKTME is a memory only package or a package
with no online CPUs. Key creation with unsafe topologies will fail
with EINVAL and a warning will be logged one time.
For example:
	[ ] MKTME: no online CPU in proximity domain
	[ ] MKTME: topology does not support key creation

These are recoverable errors. CPUs may be brought online that are
capable of programming a previously unprogrammable memory controller,
or an unprogrammable memory controller may be removed from the
platform.

Signed-off-by: Alison Schofield <alison.schofield@...el.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 security/keys/mktme_keys.c | 39 ++++++++++++++++++++++++++++++--------
 1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/security/keys/mktme_keys.c b/security/keys/mktme_keys.c
index f5fc6cccc81b..734e1d28eb24 100644
--- a/security/keys/mktme_keys.c
+++ b/security/keys/mktme_keys.c
@@ -26,6 +26,7 @@ cpumask_var_t mktme_leadcpus;		/* One lead CPU per pconfig target */
 static bool mktme_storekeys;		/* True if key payloads may be stored */
 unsigned long *mktme_bitmap_user_type;	/* Shows presence of user type keys */
 struct mktme_payload *mktme_key_store;	/* Payload storage if allowed */
+bool mktme_allow_keys;			/* True when topology supports keys */
 
 /* 1:1 Mapping between Userspace Keys (struct key) and Hardware KeyIDs */
 struct mktme_mapping {
@@ -278,33 +279,55 @@ static void mktme_destroy_key(struct key *key)
 	percpu_ref_kill(&encrypt_count[keyid]);
 }
 
+static void mktme_update_pconfig_targets(void);
 /* Key Service Method to create a new key. Payload is preparsed. */
 int mktme_instantiate_key(struct key *key, struct key_preparsed_payload *prep)
 {
 	struct mktme_payload *payload = prep->payload.data[0];
 	unsigned long flags;
+	int ret = -ENOKEY;
 	int keyid;
 
 	spin_lock_irqsave(&mktme_lock, flags);
+
+	/* Topology supports key creation */
+	if (mktme_allow_keys)
+		goto get_key;
+
+	/* Topology unknown, check it. */
+	if (!mktme_hmat_evaluate()) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	/* Keys are now allowed. Update the programming targets. */
+	mktme_update_pconfig_targets();
+	mktme_allow_keys = true;
+
+get_key:
 	keyid = mktme_reserve_keyid(key);
 	spin_unlock_irqrestore(&mktme_lock, flags);
 	if (!keyid)
-		return -ENOKEY;
+		goto out;
 
 	if (percpu_ref_init(&encrypt_count[keyid], mktme_percpu_ref_release,
 			    0, GFP_KERNEL))
-		goto err_out;
+		goto out_free_key;
 
-	if (!mktme_program_keyid(keyid, payload)) {
-		mktme_store_payload(keyid, payload);
-		return MKTME_PROG_SUCCESS;
-	}
+	ret = mktme_program_keyid(keyid, payload);
+	if (ret == MKTME_PROG_SUCCESS)
+		goto out;
+
+	/* Key programming failed */
 	percpu_ref_exit(&encrypt_count[keyid]);
-err_out:
+
+out_free_key:
 	spin_lock_irqsave(&mktme_lock, flags);
 	mktme_release_keyid(keyid);
+out_unlock:
 	spin_unlock_irqrestore(&mktme_lock, flags);
-	return -ENOKEY;
+out:
+	return ret;
 }
 
 /* Make sure arguments are correct for the TYPE of key requested */
-- 
2.20.1