2 files changed, 55 insertions, 4 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 0d79a88f4de9..e4f84f013b57 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1686,6 +1686,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         The default is to send the implementation identification
                         information.
 
+        nfsd.nfs4_disable_idmapping=
+                        [NFSv4] When set to the default of '1', the NFSv4
+                        server will return only numeric uids and gids to
+                        clients using auth_sys, and will accept numeric uids
+                        and gids from such clients.  This is intended to ease
+                        migration from NFSv2/v3.
 
         objlayoutdriver.osd_login_prog=
                         [NFS] [OBJLAYOUT] sets the pathname to the program which
diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
index 94096273cd6c..69ca9c5bb600 100644
--- a/fs/nfsd/nfs4idmap.c
+++ b/fs/nfsd/nfs4idmap.c
@@ -41,6 +41,14 @@
 #include "nfsd.h"
 
 /*
+ * Turn off idmapping when using AUTH_SYS.
+ */
+static bool nfs4_disable_idmapping = true;
+module_param(nfs4_disable_idmapping, bool, 0644);
+MODULE_PARM_DESC(nfs4_disable_idmapping,
+                "Turn off server's NFSv4 idmapping when using 'sec=sys'");
+
+/*
  * Cache entry
  */
 
@@ -561,28 +569,65 @@ idmap_id_to_name(struct svc_rqst *rqstp, int type, uid_t id, char *name)
         return ret;
 }
 
+static bool
+numeric_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namelen, uid_t *id)
+{
+        int ret;
+        char buf[11];
+
+        if (namelen + 1 > sizeof(buf))
+                /* too long to represent a 32-bit id: */
+                return false;
+        /* Just to make sure it's null-terminated: */
+        memcpy(buf, name, namelen);
+        buf[namelen] = '\0';
+        ret = strict_strtoul(name, 10, (unsigned long *)id);
+        return ret == 0;
+}
+
+static __be32
+do_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namelen, uid_t *id)
+{
+        if (nfs4_disable_idmapping && rqstp->rq_flavor < RPC_AUTH_GSS)
+                if (numeric_name_to_id(rqstp, type, name, namelen, id))
+                        return 0;
+                /*
+                 * otherwise, fall through and try idmapping, for
+                 * backwards compatibility with clients sending names:
+                 */
+        return idmap_name_to_id(rqstp, type, name, namelen, id);
+}
+
+static int
+do_id_to_name(struct svc_rqst *rqstp, int type, uid_t id, char *name)
+{
+        if (nfs4_disable_idmapping && rqstp->rq_flavor < RPC_AUTH_GSS)
+                return sprintf(name, "%u", id);
+        return idmap_id_to_name(rqstp, type, id, name);
+}
+
 __be32
 nfsd_map_name_to_uid(struct svc_rqst *rqstp, const char *name, size_t namelen,
                 __u32 *id)
 {
-        return idmap_name_to_id(rqstp, IDMAP_TYPE_USER, name, namelen, id);
+        return do_name_to_id(rqstp, IDMAP_TYPE_USER, name, namelen, id);
 }
 
 __be32
 nfsd_map_name_to_gid(struct svc_rqst *rqstp, const char *name, size_t namelen,
                 __u32 *id)
 {
-        return idmap_name_to_id(rqstp, IDMAP_TYPE_GROUP, name, namelen, id);
+        return do_name_to_id(rqstp, IDMAP_TYPE_GROUP, name, namelen, id);
 }
 
 int
 nfsd_map_uid_to_name(struct svc_rqst *rqstp, __u32 id, char *name)
 {
-        return idmap_id_to_name(rqstp, IDMAP_TYPE_USER, id, name);
+        return do_id_to_name(rqstp, IDMAP_TYPE_USER, id, name);
 }
 
 int
 nfsd_map_gid_to_name(struct svc_rqst *rqstp, __u32 id, char *name)
 {
-        return idmap_id_to_name(rqstp, IDMAP_TYPE_GROUP, id, name);
+        return do_id_to_name(rqstp, IDMAP_TYPE_GROUP, id, name);
 }