NFSv4: Fix the string length returned by the idmapper

Functions like nfs_map_uid_to_name() and nfs_map_gid_to_group() are
expected to return a string without any terminating NUL character.
Regression introduced by commit 57e62324e469e092ecc6c94a7a86fe4bd6ac5172
(NFS: Store the legacy idmapper result in the keyring).

Reported-by: Dave Chiluk <dave.chiluk@canonical.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Bryan Schumaker <bjschuma@netapp.com>
Cc: stable@vger.kernel.org [>=3.4]

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index dc0f98dfa717..c516da5873fd 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -726,9 +726,9 @@ out1:
         return ret;
 }
 
-static int nfs_idmap_instantiate(struct key *key, struct key *authkey, char *data)
+static int nfs_idmap_instantiate(struct key *key, struct key *authkey, char *data, size_t datalen)
 {
-        return key_instantiate_and_link(key, data, strlen(data) + 1,
+        return key_instantiate_and_link(key, data, datalen,
                                         id_resolver_cache->thread_keyring,
                                         authkey);
 }
@@ -738,6 +738,7 @@ static int nfs_idmap_read_and_verify_message(struct idmap_msg *im,
                 struct key *key, struct key *authkey)
 {
         char id_str[NFS_UINT_MAXLEN];
+        size_t len;
         int ret = -ENOKEY;
 
         /* ret = -ENOKEY */
@@ -747,13 +748,15 @@ static int nfs_idmap_read_and_verify_message(struct idmap_msg *im,
         case IDMAP_CONV_NAMETOID:
                 if (strcmp(upcall->im_name, im->im_name) != 0)
                         break;
-                sprintf(id_str, "%d", im->im_id);
-                ret = nfs_idmap_instantiate(key, authkey, id_str);
+                /* Note: here we store the NUL terminator too */
+                len = sprintf(id_str, "%d", im->im_id) + 1;
+                ret = nfs_idmap_instantiate(key, authkey, id_str, len);
                 break;
         case IDMAP_CONV_IDTONAME:
                 if (upcall->im_id != im->im_id)
                         break;
-                ret = nfs_idmap_instantiate(key, authkey, im->im_name);
+                len = strlen(im->im_name);
+                ret = nfs_idmap_instantiate(key, authkey, im->im_name, len);
                 break;
         default:
                 ret = -EINVAL;