NFSv3: match sec= flavor against server list
Older linux clients match the 'sec=' mount option flavor against the server's
flavor list (if available) and return EPERM if the specified flavor or AUTH_NULL
(which "matches" any flavor) is not found.
Recent changes skip this step and allow the vfs mount even though no operations
will succeed, creating a 'dud' mount.
This patch reverts back to the old behavior of matching specified flavors
against the server list and also returns EPERM when no sec= is specified and
none of the flavors returned by the server are supported by the client.
Example of behavior change:
the server's /etc/exports:
/export/krb5 *(sec=krb5,rw,no_root_squash)
old client behavior:
$ uname -a
Linux one.apikia.fake 3.8.8-202.fc18.x86_64 #1 SMP Wed Apr 17 23:25:17 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
$ sudo mount -v -o sec=sys,vers=3 zero:/export/krb5 /mnt
mount.nfs: timeout set for Sun May 5 17:32:04 2013
mount.nfs: trying text-based options 'sec=sys,vers=3,addr=192.168.100.10'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 192.168.100.10 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 192.168.100.10 prog 100005 vers 3 prot UDP port 20048
mount.nfs: mount(2): Permission denied
mount.nfs: access denied by server while mounting zero:/export/krb5
recently changed behavior:
$ uname -a
Linux one.apikia.fake 3.9.0-testing+ #2 SMP Fri May 3 20:29:32 EDT 2013 x86_64 x86_64 x86_64 GNU/Linux
$ sudo mount -v -o sec=sys,vers=3 zero:/export/krb5 /mnt
mount.nfs: timeout set for Sun May 5 17:37:17 2013
mount.nfs: trying text-based options 'sec=sys,vers=3,addr=192.168.100.10'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 192.168.100.10 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 192.168.100.10 prog 100005 vers 3 prot UDP port 20048
$ ls /mnt
ls: cannot open directory /mnt: Permission denied
$ sudo ls /mnt
ls: cannot open directory /mnt: Permission denied
$ sudo df /mnt
df: ‘/mnt’: Permission denied
df: no file systems processed
$ sudo umount /mnt
$
Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 3bb8318..b65001c 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1607,16 +1607,15 @@
/*
* Select a security flavor for this mount. The selected flavor
* is planted in args->auth_flavors[0].
+ *
+ * Returns 0 on success, -EACCES on failure.
*/
-static void nfs_select_flavor(struct nfs_parsed_mount_data *args,
+static int nfs_select_flavor(struct nfs_parsed_mount_data *args,
struct nfs_mount_request *request)
{
unsigned int i, count = *(request->auth_flav_len);
rpc_authflavor_t flavor;
- if (args->auth_flavors[0] != RPC_AUTH_MAXFLAVOR)
- goto out;
-
/*
* The NFSv2 MNT operation does not return a flavor list.
*/
@@ -1631,6 +1630,25 @@
goto out_default;
/*
+ * If the sec= mount option is used, the specified flavor or AUTH_NULL
+ * must be in the list returned by the server.
+ *
+ * AUTH_NULL has a special meaning when it's in the server list - it
+ * means that the server will ignore the rpc creds, so any flavor
+ * can be used.
+ */
+ if (args->auth_flavors[0] != RPC_AUTH_MAXFLAVOR) {
+ for (i = 0; i < count; i++) {
+ if (args->auth_flavors[0] == request->auth_flavs[i] ||
+ request->auth_flavs[i] == RPC_AUTH_NULL)
+ goto out;
+ }
+ dfprintk(MOUNT, "NFS: auth flavor %d not supported by server\n",
+ args->auth_flavors[0]);
+ goto out_err;
+ }
+
+ /*
* RFC 2623, section 2.7 suggests we SHOULD prefer the
* flavor listed first. However, some servers list
* AUTH_NULL first. Avoid ever choosing AUTH_NULL.
@@ -1650,12 +1668,29 @@
}
}
+ /*
+ * As a last chance, see if the server list contains AUTH_NULL -
+ * if it does, use the default flavor.
+ */
+ for (i = 0; i < count; i++) {
+ if (request->auth_flavs[i] == RPC_AUTH_NULL)
+ goto out_default;
+ }
+
+ dfprintk(MOUNT, "NFS: no auth flavors in common with server\n");
+ goto out_err;
+
out_default:
- flavor = RPC_AUTH_UNIX;
+ /* use default if flavor not already set */
+ flavor = (args->auth_flavors[0] == RPC_AUTH_MAXFLAVOR) ?
+ RPC_AUTH_UNIX : args->auth_flavors[0];
out_set:
args->auth_flavors[0] = flavor;
out:
dfprintk(MOUNT, "NFS: using auth flavor %d\n", args->auth_flavors[0]);
+ return 0;
+out_err:
+ return -EACCES;
}
/*
@@ -1718,8 +1753,7 @@
return status;
}
- nfs_select_flavor(args, &request);
- return 0;
+ return nfs_select_flavor(args, &request);
}
struct dentry *nfs_try_mount(int flags, const char *dev_name,