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>

2 files changed, 18 insertions, 3 deletions

diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c
index 6e92b0fe532..cf61dc8ae94 100644
--- a/fs/nfsd/auth.c
+++ b/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;
diff --git a/include/linux/nfsd/export.h b/include/linux/nfsd/export.h
index a01f775cb94..78feb7beff7 100644
--- a/include/linux/nfsd/export.h
+++ b/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__