v4.19.13 snapshot.
diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c
new file mode 100644
index 0000000..fdf2aad
--- /dev/null
+++ b/fs/nfsd/auth.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de> */
+
+#include <linux/sched.h>
+#include "nfsd.h"
+#include "auth.h"
+
+int nfsexp_flags(struct svc_rqst *rqstp, struct svc_export *exp)
+{
+ struct exp_flavor_info *f;
+ struct exp_flavor_info *end = exp->ex_flavors + exp->ex_nflavors;
+
+ for (f = exp->ex_flavors; f < end; f++) {
+ if (f->pseudoflavor == rqstp->rq_cred.cr_flavor)
+ return f->flags;
+ }
+ return exp->ex_flags;
+
+}
+
+int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp)
+{
+ struct group_info *rqgi;
+ struct group_info *gi;
+ struct cred *new;
+ int i;
+ int flags = nfsexp_flags(rqstp, exp);
+
+ validate_process_creds();
+
+ /* discard any old override before preparing the new set */
+ revert_creds(get_cred(current_real_cred()));
+ new = prepare_creds();
+ if (!new)
+ return -ENOMEM;
+
+ new->fsuid = rqstp->rq_cred.cr_uid;
+ new->fsgid = rqstp->rq_cred.cr_gid;
+
+ rqgi = rqstp->rq_cred.cr_group_info;
+
+ if (flags & NFSEXP_ALLSQUASH) {
+ new->fsuid = exp->ex_anon_uid;
+ new->fsgid = exp->ex_anon_gid;
+ gi = groups_alloc(0);
+ if (!gi)
+ goto oom;
+ } else if (flags & NFSEXP_ROOTSQUASH) {
+ if (uid_eq(new->fsuid, GLOBAL_ROOT_UID))
+ new->fsuid = exp->ex_anon_uid;
+ if (gid_eq(new->fsgid, GLOBAL_ROOT_GID))
+ new->fsgid = exp->ex_anon_gid;
+
+ gi = groups_alloc(rqgi->ngroups);
+ if (!gi)
+ goto oom;
+
+ for (i = 0; i < rqgi->ngroups; i++) {
+ if (gid_eq(GLOBAL_ROOT_GID, rqgi->gid[i]))
+ gi->gid[i] = exp->ex_anon_gid;
+ else
+ gi->gid[i] = rqgi->gid[i];
+ }
+
+ /* Each thread allocates its own gi, no race */
+ groups_sort(gi);
+ } else {
+ gi = get_group_info(rqgi);
+ }
+
+ if (uid_eq(new->fsuid, INVALID_UID))
+ new->fsuid = exp->ex_anon_uid;
+ if (gid_eq(new->fsgid, INVALID_GID))
+ new->fsgid = exp->ex_anon_gid;
+
+ set_groups(new, gi);
+ put_group_info(gi);
+
+ if (!uid_eq(new->fsuid, GLOBAL_ROOT_UID))
+ new->cap_effective = cap_drop_nfsd_set(new->cap_effective);
+ else
+ new->cap_effective = cap_raise_nfsd_set(new->cap_effective,
+ new->cap_permitted);
+ validate_process_creds();
+ put_cred(override_creds(new));
+ put_cred(new);
+ validate_process_creds();
+ return 0;
+
+oom:
+ abort_creds(new);
+ return -ENOMEM;
+}
+