nfsd: restrict filehandles accepted in V4ROOT case

[safe/jmp/linux-2.6] / fs / nfsd / nfsfh.c

diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 951938d..44812c3 100644 (file)
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -103,6 +103,36 @@ static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
        return nfserrno(nfsd_setuser(rqstp, exp));
 }
 
+static inline __be32 check_pseudo_root(struct svc_rqst *rqstp,
+       struct dentry *dentry, struct svc_export *exp)
+{
+       if (!(exp->ex_flags & NFSEXP_V4ROOT))
+               return nfs_ok;
+       /*
+        * v2/v3 clients have no need for the V4ROOT export--they use
+        * the mount protocl instead; also, further V4ROOT checks may be
+        * in v4-specific code, in which case v2/v3 clients could bypass
+        * them.
+        */
+       if (!nfsd_v4client(rqstp))
+               return nfserr_stale;
+       /*
+        * We're exposing only the directories and symlinks that have to be
+        * traversed on the way to real exports:
+        */
+       if (unlikely(!S_ISDIR(dentry->d_inode->i_mode) &&
+                    !S_ISLNK(dentry->d_inode->i_mode)))
+               return nfserr_stale;
+       /*
+        * A pseudoroot export gives permission to access only one
+        * single directory; the kernel has to make another upcall
+        * before granting access to anything else under it:
+        */
+       if (unlikely(dentry != exp->ex_path.dentry))
+               return nfserr_stale;
+       return nfs_ok;
+}
+
 /*
  * Use the given filehandle to look up the corresponding export and
  * dentry.  On success, the results are used to set fh_export and
@@ -299,6 +329,10 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
         *        (for example, if different id-squashing options are in
         *        effect on the new filesystem).
         */
+       error = check_pseudo_root(rqstp, dentry, exp);
+       if (error)
+               goto out;
+
        error = nfsd_setuser_and_check_port(rqstp, exp);
        if (error)
                goto out;