SUNRPC: add 'struct cred *' to auth_cred and rpc_cred

The SUNRPC credential framework was put together before
Linux has 'struct cred'.  Now that we have it, it makes sense to
use it.
This first step just includes a suitable 'struct cred *' pointer
in every 'struct auth_cred' and almost every 'struct rpc_cred'.

The rpc_cred used for auth_null has a NULL 'struct cred *' as nothing
else really makes sense.

For rpc_cred, the pointer is reference counted.
For auth_cred it isn't.  struct auth_cred are either allocated on
the stack, in which case the thread owns a reference to the auth,
or are part of 'struct generic_cred' in which case gc_base owns the
reference, and "acred" shares it.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

2 files changed, 29 insertions, 1 deletions

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index 310d7500f665..22e164106333 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -9,6 +9,7 @@
 #include <linux/nfs_fs.h>
 #include <linux/nfs_page.h>
 #include <linux/module.h>
+#include <linux/sched/mm.h>
 
 #include <linux/sunrpc/metrics.h>
 
@@ -415,6 +416,7 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 		struct nfs4_ff_layout_mirror *mirror;
 		struct auth_cred acred = { .group_info = ff_zero_group };
 		struct rpc_cred	__rcu *cred;
+		struct cred *kcred;
 		u32 ds_count, fh_count, id;
 		int j;
 
@@ -491,8 +493,23 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 
 		acred.gid = make_kgid(&init_user_ns, id);
 
+		if (gfp_flags & __GFP_FS)
+			kcred = prepare_kernel_cred(NULL);
+		else {
+			unsigned int nofs_flags = memalloc_nofs_save();
+			kcred = prepare_kernel_cred(NULL);
+			memalloc_nofs_restore(nofs_flags);
+		}
+		rc = -ENOMEM;
+		if (!kcred)
+			goto out_err_free;
+		kcred->fsuid = acred.uid;
+		kcred->fsgid = acred.gid;
+		acred.cred = kcred;
+
 		/* find the cred for it */
 		rcu_assign_pointer(cred, rpc_lookup_generic_cred(&acred, 0, gfp_flags));
+		put_cred(kcred);
 		if (IS_ERR(cred)) {
 			rc = PTR_ERR(cred);
 			goto out_err_free;
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 25987bcdf96f..7c7e3510599d 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -858,10 +858,21 @@ static struct rpc_cred *get_backchannel_cred(struct nfs4_client *clp, struct rpc
 	} else {
 		struct rpc_auth *auth = client->cl_auth;
 		struct auth_cred acred = {};
+		struct cred *kcred;
+		struct rpc_cred *ret;
+
+		kcred = prepare_kernel_cred(NULL);
+		if (!kcred)
+			return NULL;
 
 		acred.uid = ses->se_cb_sec.uid;
 		acred.gid = ses->se_cb_sec.gid;
-		return auth->au_ops->lookup_cred(client->cl_auth, &acred, 0);
+		kcred->uid = acred.uid;
+		kcred->gid = acred.gid;
+		acred.cred = kcred;
+		ret = auth->au_ops->lookup_cred(client->cl_auth, &acred, 0);
+		put_cred(kcred);
+		return ret;
 	}
 }