[PATCH v12 1/6] s390/cert_store: Pin the user session keyring

[Jarkko Sakkinen <jarkko@kernel.org>]

The user session keyring stays alive only because the session keyring is
pinned by current_cred().

Pin the reference at:

1. find_cs_keyring()
2. cleanup_cs_keys()
3. create_cs_keyring()

Cc: David Howells <dhowells@redhat.com>
Cc: stable@vger.kernel.org # v6.1+
Fixes: 8cf57d7217c3 ("s390: add support for user-defined certificates")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 arch/s390/kernel/cert_store.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kernel/cert_store.c b/arch/s390/kernel/cert_store.c
index 998f2da56175..bb218b42a2c9 100644
--- a/arch/s390/kernel/cert_store.c
+++ b/arch/s390/kernel/cert_store.c
@@ -307,7 +307,6 @@ static struct key *get_user_session_keyring(void)
 			   PTR_ERR(us_keyring_ref));
 		return ERR_PTR(-ENOKEY);
 	}
-	key_ref_put(us_keyring_ref);
 	return key_ref_to_ptr(us_keyring_ref);
 }
 
@@ -352,11 +351,17 @@ static int invalidate_keyring_keys(struct key *keyring)
 static struct key *find_cs_keyring(void)
 {
 	key_ref_t cs_keyring_ref;
+	struct key *us_keyring;
 	struct key *cs_keyring;
 
-	cs_keyring_ref = keyring_search(make_key_ref(get_user_session_keyring(), true),
+	us_keyring = get_user_session_keyring();
+	if (IS_ERR(us_keyring))
+		return NULL;
+
+	cs_keyring_ref = keyring_search(make_key_ref(us_keyring, true),
 					&key_type_keyring, CERT_STORE_KEYRING_NAME,
 					false);
+	key_put(us_keyring);
 	if (!IS_ERR(cs_keyring_ref)) {
 		cs_keyring = key_ref_to_ptr(cs_keyring_ref);
 		key_ref_put(cs_keyring_ref);
@@ -373,6 +378,7 @@ static struct key *find_cs_keyring(void)
 
 static void cleanup_cs_keys(void)
 {
+	struct key *us_keyring;
 	struct key *cs_keyring;
 
 	cs_keyring = find_cs_keyring();
@@ -390,20 +396,33 @@ static void cleanup_cs_keys(void)
 	keyring_clear(cs_keyring);
 	key_invalidate(cs_keyring);
 	key_put(cs_keyring);
-	key_unlink(get_user_session_keyring(), cs_keyring);
+
+	us_keyring = get_user_session_keyring();
+	if (IS_ERR(us_keyring))
+		return;
+
+	key_unlink(us_keyring, cs_keyring);
+	key_put(us_keyring);
 }
 
 static struct key *create_cs_keyring(void)
 {
 	static struct key *cs_keyring;
+	struct key *us_keyring;
 
 	/* Cleanup previous cs_keyring and all associated keys if any. */
 	cleanup_cs_keys();
+
+	us_keyring = get_user_session_keyring();
+	if (IS_ERR(us_keyring))
+		return NULL;
+
 	cs_keyring = keyring_alloc(CERT_STORE_KEYRING_NAME, GLOBAL_ROOT_UID,
 				   GLOBAL_ROOT_GID, current_cred(),
 				   (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ,
 				   KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_SET_KEEP,
-				   NULL, get_user_session_keyring());
+				   NULL, us_keyring);
+	key_put(us_keyring);
 	if (IS_ERR(cs_keyring)) {
 		pr_dbf_msg("Can't allocate cert_store keyring");
 		return NULL;
-- 
2.47.3