knfsd: nfsd: enforce per-flavor id squashing

Allow root squashing to vary per-pseudoflavor, so that you can (for example)
allow root access only when sufficiently strong security is in use.

Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nfsd/auth.c

@@ -12,17 +12,31 @@
 
 #define	CAP_NFSD_MASK (CAP_FS_MASK|CAP_TO_MASK(CAP_SYS_RESOURCE))
 
+static 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_flavor)
+			return f->flags;
+	}
+	return exp->ex_flags;
+
+}
+
 int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp)
 {
 	struct svc_cred	cred = rqstp->rq_cred;
 	int i;
+	int flags = nfsexp_flags(rqstp, exp);
 	int ret;
 
-	if (exp->ex_flags & NFSEXP_ALLSQUASH) {
+	if (flags & NFSEXP_ALLSQUASH) {
 		cred.cr_uid = exp->ex_anon_uid;
 		cred.cr_gid = exp->ex_anon_gid;
 		cred.cr_group_info = groups_alloc(0);
-	} else if (exp->ex_flags & NFSEXP_ROOTSQUASH) {
+	} else if (flags & NFSEXP_ROOTSQUASH) {
 		struct group_info *gi;
 		if (!cred.cr_uid)
 			cred.cr_uid = exp->ex_anon_uid;

include/linux/nfsd/export.h

@@ -43,7 +43,8 @@
 #define NFSEXP_ALLFLAGS		0xFE3F
 
 /* The flags that may vary depending on security flavor: */
-#define NFSEXP_SECINFO_FLAGS	0
+#define NFSEXP_SECINFO_FLAGS	(NFSEXP_READONLY | NFSEXP_ROOTSQUASH \
+					| NFSEXP_ALLSQUASH)
 
 #ifdef __KERNEL__