linux-kernel - [PATCHv2 38/59] keys/mktme: Do not allow key creation in unsafe topologies

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Date:   Wed, 31 Jul 2019 18:07:52 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
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: [PATCHv2 38/59] keys/mktme: Do not allow key creation in unsafe topologies

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

MKTME 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.

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 | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/security/keys/mktme_keys.c b/security/keys/mktme_keys.c
index 6265b62801e9..70662e882674 100644
--- a/security/keys/mktme_keys.c
+++ b/security/keys/mktme_keys.c
@@ -23,6 +23,7 @@ static unsigned int mktme_available_keyids;  /* Free Hardware KeyIDs */
 static struct kmem_cache *mktme_prog_cache;  /* Hardware programming cache */
 static unsigned long *mktme_target_map;	     /* PCONFIG programming target */
 static cpumask_var_t mktme_leadcpus;	     /* One CPU per PCONFIG target */
+static bool mktme_allow_keys;		     /* HW topology supports keys */
 
 enum mktme_keyid_state {
 	KEYID_AVAILABLE,	/* Available to be assigned */
@@ -253,32 +254,55 @@ 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)
 {
 	u32 *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))
-		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 */
-- 
2.21.0