From d688f7b8f62857c252b886fa16e8b38b83cfaf7e Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Wed, 24 Jul 2013 12:28:28 -0400 Subject: [PATCH] NFS: Use root's credential for lease management when keytab is missing Commit 05f4c350 "NFS: Discover NFSv4 server trunking when mounting" Fri Sep 14 17:24:32 2012 introduced Uniform Client String support, which forces our NFS client to establish a client ID immediately during a mount operation rather than waiting until a user wants to open a file. Normally machine credentials (eg. from a keytab) are used to perform a mount operation that is protected by Kerberos. Before 05fc350, SETCLIENTID used a machine credential, or fell back to a regular user's credential if no keytab is available. On clients that don't have a keytab, performing SETCLIENTID early means there's no user credential to fall back on, since no regular user has kinit'd yet. 05f4c350 seems to have broken the ability to mount with sec=krb5 on clients that don't have a keytab in kernels 3.7 - 3.10. To address this regression, commit 4edaa308 (NFS: Use "krb5i" to establish NFSv4 state whenever possible), Sat Mar 16 15:56:20 2013, was merged in 3.10. This commit forces the NFS client to fall back to AUTH_SYS for lease management operations if no keytab is available. Neil Brown noticed that, since root is required to kinit to do a sec=krb5 mount when a client doesn't have a keytab, we can try to use root's Kerberos credential before AUTH_SYS. Now, when determining a principal and flavor to use for lease management, the NFS client tries in this order: 1. Flavor: AUTH_GSS, krb5i Principal: service principal (via keytab) 2. Flavor: AUTH_GSS, krb5i Principal: user principal established for UID 0 (via kinit) 3. Flavor: AUTH_SYS Principal: UID 0 / GID 0 Signed-off-by: Chuck Lever Signed-off-by: Trond Myklebust --- fs/nfs/nfs4state.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index ad1a7533ce6d..f27760b1b06f 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -154,6 +154,19 @@ struct rpc_cred *nfs4_get_machine_cred_locked(struct nfs_client *clp) return cred; } +static void nfs4_root_machine_cred(struct nfs_client *clp) +{ + struct rpc_cred *cred, *new; + + new = rpc_lookup_machine_cred(NULL); + spin_lock(&clp->cl_lock); + cred = clp->cl_machine_cred; + clp->cl_machine_cred = new; + spin_unlock(&clp->cl_lock); + if (cred != NULL) + put_rpccred(cred); +} + static struct rpc_cred * nfs4_get_renew_cred_server_locked(struct nfs_server *server) { @@ -1896,7 +1909,11 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, __func__, status); goto again; case -EACCES: - if (i++) + if (i++ == 0) { + nfs4_root_machine_cred(clp); + goto again; + } + if (i > 2) break; case -NFS4ERR_CLID_INUSE: case -NFS4ERR_WRONGSEC: -- GitLab