linux-kernel - [PATCH 02/10] keys: sparse: Fix incorrect RCU accesses [ver #3]

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Message-ID: <156095034027.9363.14636937467673662369.stgit@warthog.procyon.org.uk>
Date:   Wed, 19 Jun 2019 14:19:00 +0100
From:   David Howells <dhowells@...hat.com>
To:     keyrings@...r.kernel.org, ebiggers@...nel.org
Cc:     James Morris <jamorris@...ux.microsoft.com>, dhowells@...hat.com,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 02/10] keys: sparse: Fix incorrect RCU accesses [ver #3]

Fix a pair of accesses that should be using RCU protection.

rcu_dereference_protected() is needed to access task_struct::real_parent.

current_cred() should be used to access current->cred.

Signed-off-by: David Howells <dhowells@...hat.com>
Reviewed-by: James Morris <jamorris@...ux.microsoft.com>
---

 security/keys/keyctl.c           |    3 ++-
 security/keys/request_key_auth.c |    2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 3e4053a217c3..0f947bcbad46 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1524,7 +1524,8 @@ long keyctl_session_to_parent(void)
 
 	ret = -EPERM;
 	oldwork = NULL;
-	parent = me->real_parent;
+	parent = rcu_dereference_protected(me->real_parent,
+					   lockdep_is_held(&tasklist_lock));
 
 	/* the parent mustn't be init and mustn't be a kernel thread */
 	if (parent->pid <= 1 || !parent->mm)
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index bda6201c6c45..572c7a60473a 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -152,7 +152,7 @@ struct key *request_key_auth_new(struct key *target, const char *op,
 				 struct key *dest_keyring)
 {
 	struct request_key_auth *rka, *irka;
-	const struct cred *cred = current->cred;
+	const struct cred *cred = current_cred();
 	struct key *authkey = NULL;
 	char desc[20];
 	int ret = -ENOMEM;