linux-kernel - [PATCH v2 5/5] eCryptfs: write lock requested keys

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Date:	Mon, 21 Mar 2011 16:00:55 +0100
From:	Roberto Sassu <roberto.sassu@...ito.it>
To:	tyhicks@...ux.vnet.ibm.com
Cc:	kirkland@...onical.com, dhowells@...hat.com, jmorris@...ei.org,
	linux-fsdevel@...r.kernel.org, keyrings@...ux-nfs.org,
	linux-kernel@...r.kernel.org, ecryptfs-devel@...ts.launchpad.net,
	Roberto Sassu <roberto.sassu@...ito.it>
Subject: [PATCH v2 5/5] eCryptfs: write lock requested keys

A requested key is write locked in order to prevent modifications on the
authentication token while it is being used.

Signed-off-by: Roberto Sassu <roberto.sassu@...ito.it>
---
 fs/ecryptfs/keystore.c |   26 ++++++++++++++++++++------
 fs/ecryptfs/main.c     |    4 +++-
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 09b3afe..455ce8f 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -522,10 +522,11 @@ ecryptfs_find_global_auth_tok_for_sig(
 				goto out_invalid_auth_tok;
 		}
 
+		down_write(&(walker->global_auth_tok_key->sem));
 		rc = ecryptfs_verify_auth_tok_from_key(
 				walker->global_auth_tok_key, auth_tok);
 		if (rc)
-			goto out_invalid_auth_tok;
+			goto out_invalid_auth_tok_unlock;
 
 		(*auth_tok_key) = walker->global_auth_tok_key;
 		key_get(*auth_tok_key);
@@ -534,6 +535,8 @@ ecryptfs_find_global_auth_tok_for_sig(
 	rc = -ENOENT;
 	goto out;
 
+out_invalid_auth_tok_unlock:
+	up_write(&(walker->global_auth_tok_key->sem));
 out_invalid_auth_tok:
 	printk(KERN_WARNING "Invalidating auth tok with sig = [%s]\n", sig);
 	walker->flags |= ECRYPTFS_AUTH_TOK_INVALID;
@@ -877,8 +880,10 @@ out_free_unlock:
 out_unlock:
 	mutex_unlock(s->tfm_mutex);
 out:
-	if (auth_tok_key)
+	if (auth_tok_key) {
+		up_write(&(auth_tok_key->sem));
 		key_put(auth_tok_key);
+	}
 	kfree(s);
 	return rc;
 }
@@ -1114,8 +1119,10 @@ out:
 		(*filename_size) = 0;
 		(*filename) = NULL;
 	}
-	if (auth_tok_key)
+	if (auth_tok_key) {
+		up_write(&(auth_tok_key->sem));
 		key_put(auth_tok_key);
+	}
 	kfree(s);
 	return rc;
 }
@@ -1646,9 +1653,10 @@ int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
 		(*auth_tok_key) = NULL;
 		goto out;
 	}
-
+	down_write(&(*auth_tok_key)->sem);
 	rc = ecryptfs_verify_auth_tok_from_key(*auth_tok_key, auth_tok);
 	if (rc) {
+		up_write(&(*auth_tok_key)->sem);
 		key_put(*auth_tok_key);
 		(*auth_tok_key) = NULL;
 		goto out;
@@ -1873,6 +1881,7 @@ int ecryptfs_parse_packet_set(struct ecryptfs_crypt_stat *crypt_stat,
 find_next_matching_auth_tok:
 	found_auth_tok = 0;
 	if (auth_tok_key) {
+		up_write(&(auth_tok_key->sem));
 		key_put(auth_tok_key);
 		auth_tok_key = NULL;
 	}
@@ -1959,8 +1968,10 @@ found_matching_auth_tok:
 out_wipe_list:
 	wipe_auth_tok_list(&auth_tok_list);
 out:
-	if (auth_tok_key)
+	if (auth_tok_key) {
+		up_write(&(auth_tok_key->sem));
 		key_put(auth_tok_key);
+	}
 	return rc;
 }
 
@@ -2455,6 +2466,7 @@ ecryptfs_generate_key_packet_set(char *dest_base,
 			rc = -EINVAL;
 			goto out_free;
 		}
+		up_write(&(auth_tok_key->sem));
 		key_put(auth_tok_key);
 		auth_tok_key = NULL;
 	}
@@ -2469,8 +2481,10 @@ out_free:
 out:
 	if (rc)
 		(*len) = 0;
-	if (auth_tok_key)
+	if (auth_tok_key) {
+		up_write(&(auth_tok_key->sem));
 		key_put(auth_tok_key);
+	}
 
 	mutex_unlock(&crypt_stat->keysig_list_mutex);
 	return rc;
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index f079473..ada50a3 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -256,8 +256,10 @@ static int ecryptfs_init_global_auth_toks(
 			       "option: [%s]\n", global_auth_tok->sig);
 			global_auth_tok->flags |= ECRYPTFS_AUTH_TOK_INVALID;
 			goto out;
-		} else
+		} else {
 			global_auth_tok->flags &= ~ECRYPTFS_AUTH_TOK_INVALID;
+			up_write(&(global_auth_tok->global_auth_tok_key)->sem);
+		}
 	}
 out:
 	return rc;
-- 
1.7.4


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