linux-kernel - [PATCH 2/2] eCryptfs: lock requested keys for writing

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Date:	Fri, 28 Jan 2011 11:42:04 +0100
From:	Roberto Sassu <roberto.sassu@...ito.it>
To:	tyhicks@...ux.vnet.ibm.com
Cc:	kirkland@...onical.com, dhowells@...hat.com,
	keyrings@...ux-nfs.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Roberto Sassu <roberto.sassu@...ito.it>
Subject: [PATCH 2/2] eCryptfs: lock requested keys for writing

Keys requested by eCryptfs are exclusively locked in order to prevent
modifications by other subjects. In particular those which description is
specified at mount time are locked until the filesystem is unmounted, these
required to decrypt a single file are unlocked immediately after the open.

Signed-off-by: Roberto Sassu <roberto.sassu@...ito.it>
Reported-by: David Howells <dhowells@...hat.com>
---
 fs/ecryptfs/crypto.c   |    4 +++-
 fs/ecryptfs/keystore.c |   15 ++++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index bfd8b68..6b32776 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -268,8 +268,10 @@ void ecryptfs_destroy_mount_crypt_stat(
 		list_del(&auth_tok->mount_crypt_stat_list);
 		mount_crypt_stat->num_global_auth_toks--;
 		if (auth_tok->global_auth_tok_key
-		    && !(auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID))
+		    && !(auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID)) {
+			up_write(&(auth_tok->global_auth_tok_key->sem));
 			key_put(auth_tok->global_auth_tok_key);
+		}
 		kmem_cache_free(ecryptfs_global_auth_tok_cache, auth_tok);
 	}
 	mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 4feb78c..c90456a 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -765,8 +765,10 @@ 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;
 }
@@ -1002,8 +1004,10 @@ 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;
 }
@@ -1566,6 +1570,7 @@ int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
 		(*auth_tok_key) = NULL;
 		goto out;
 	}
+	down_write(&((*auth_tok_key)->sem));
 	(*auth_tok) = ecryptfs_get_key_payload_data(*auth_tok_key);
 	if (ecryptfs_verify_version((*auth_tok)->version)) {
 		printk(KERN_ERR
@@ -1587,6 +1592,7 @@ int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
 	}
 out_release_key:
 	if (rc) {
+		up_write(&((*auth_tok_key)->sem));
 		key_put(*auth_tok_key);
 		(*auth_tok_key) = NULL;
 	}
@@ -1810,6 +1816,7 @@ 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;
 	}
@@ -1896,8 +1903,10 @@ 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;
 }
 
-- 
1.7.3.4


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