Skip to contentSkip to conversation

FAILED: patch "[PATCH] ecryptfs: fix dereference of NULL user_key_payload" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Oct 24, 2017

Subsystems (2)
Stable branch Ecrypt file system
lore
Share & tools
lore

[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From f66665c09ab489a11ca490d6a82df57cfc1bea3e Mon Sep 17 00:00:00 2001

From: Eric Biggers <[email protected]>
Date: Mon, 9 Oct 2017 12:51:27 -0700
Subject: [PATCH] ecryptfs: fix dereference of NULL user_key_payload

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 <[email protected]>
Cc <[email protected]> [v2.6.19+]
Cc Michael Halcrow <[email protected]>
Signed-off-by Eric Biggers <[email protected]>
Signed-off-by David Howells <[email protected]>
fs/ecryptfs/ecryptfs_kernel.h +17 -7
index 9c351bf757b2..3fbc0ff79699 100644
@@ -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
fs/ecryptfs/keystore.c +8 -1
index 3cf1546dca82..fa218cd64f74 100644
@@ -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 key *auth_tok_key,
 	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 "