Patch "ecryptfs: fix dereference of NULL user_key_payload" has been added to the 4.13-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ecryptfs: fix dereference of NULL user_key_payload

to the 4.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ecryptfs-fix-dereference-of-null-user_key_payload.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From f66665c09ab489a11ca490d6a82df57cfc1bea3e Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Mon, 9 Oct 2017 12:51:27 -0700
Subject: ecryptfs: fix dereference of NULL user_key_payload

From: Eric Biggers <ebiggers@google.com>

commit f66665c09ab489a11ca490d6a82df57cfc1bea3e upstream.

In eCryptfs, we failed to verify that the authentication token keys are
not revoked before dereferencing their payloads, which is problematic
because the payload of a revoked key is NULL.  request_key() *does* skip
revoked keys, but there is still a window where the key can be revoked
before we acquire the key semaphore.

Fix it by updating ecryptfs_get_key_payload_data() to return
-EKEYREVOKED if the key payload is NULL.  For completeness we check this
for "encrypted" keys as well as "user" keys, although encrypted keys
cannot be revoked currently.

Alternatively we could use key_validate(), but since we'll also need to
fix ecryptfs_get_key_payload_data() to validate the payload length, it
seems appropriate to just check the payload pointer.

Fixes: 237fead61998 ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig")
Reviewed-by: James Morris <james.l.morris@oracle.com>
Cc: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ecryptfs/ecryptfs_kernel.h |   24 +++++++++++++++++-------
 fs/ecryptfs/keystore.c        |    9 ++++++++-
 2 files changed, 25 insertions(+), 8 deletions(-)

--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -84,11 +84,16 @@ struct ecryptfs_page_crypt_context {
 static inline struct ecryptfs_auth_tok *
 ecryptfs_get_encrypted_key_payload_data(struct key *key)
 {
-	if (key->type == &key_type_encrypted)
-		return (struct ecryptfs_auth_tok *)
-			(&((struct encrypted_key_payload *)key->payload.data[0])->payload_data);
-	else
+	struct encrypted_key_payload *payload;
+
+	if (key->type != &key_type_encrypted)
 		return NULL;
+
+	payload = key->payload.data[0];
+	if (!payload)
+		return ERR_PTR(-EKEYREVOKED);
+
+	return (struct ecryptfs_auth_tok *)payload->payload_data;
 }
 
 static inline struct key *ecryptfs_get_encrypted_key(char *sig)
@@ -114,12 +119,17 @@ static inline struct ecryptfs_auth_tok *
 ecryptfs_get_key_payload_data(struct key *key)
 {
 	struct ecryptfs_auth_tok *auth_tok;
+	struct user_key_payload *ukp;
 
 	auth_tok = ecryptfs_get_encrypted_key_payload_data(key);
-	if (!auth_tok)
-		return (struct ecryptfs_auth_tok *)user_key_payload_locked(key)->data;
-	else
+	if (auth_tok)
 		return auth_tok;
+
+	ukp = user_key_payload_locked(key);
+	if (!ukp)
+		return ERR_PTR(-EKEYREVOKED);
+
+	return (struct ecryptfs_auth_tok *)ukp->data;
 }
 
 #define ECRYPTFS_MAX_KEYSET_SIZE 1024
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -459,7 +459,8 @@ out:
  * @auth_tok_key: key containing the authentication token
  * @auth_tok: authentication token
  *
- * Returns zero on valid auth tok; -EINVAL otherwise
+ * Returns zero on valid auth tok; -EINVAL if the payload is invalid; or
+ * -EKEYREVOKED if the key was revoked before we acquired its semaphore.
  */
 static int
 ecryptfs_verify_auth_tok_from_key(struct key *auth_tok_key,
@@ -468,6 +469,12 @@ ecryptfs_verify_auth_tok_from_key(struct
 	int rc = 0;
 
 	(*auth_tok) = ecryptfs_get_key_payload_data(auth_tok_key);
+	if (IS_ERR(*auth_tok)) {
+		rc = PTR_ERR(*auth_tok);
+		*auth_tok = NULL;
+		goto out;
+	}
+
 	if (ecryptfs_verify_version((*auth_tok)->version)) {
 		printk(KERN_ERR "Data structure version mismatch. Userspace "
 		       "tools must match eCryptfs kernel module with major "


Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.13/keys-fix-race-between-updating-and-finding-a-negative-key.patch
queue-4.13/fs-cache-fix-dereference-of-null-user_key_payload.patch
queue-4.13/lib-digsig-fix-dereference-of-null-user_key_payload.patch
queue-4.13/ecryptfs-fix-dereference-of-null-user_key_payload.patch
queue-4.13/fscrypt-fix-dereference-of-null-user_key_payload.patch
queue-4.13/keys-encrypted-fix-dereference-of-null-user_key_payload.patch
queue-4.13/keys-don-t-let-add_key-update-an-uninstantiated-key.patch