1 files changed, 60 insertions, 42 deletions

diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 01965b2f3a76..1c12177b908c 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -1,6 +1,4 @@
 /*
- * linux/fs/nfsd/nfsfh.c
- *
  * NFS server file handle treatment.
  *
  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
@@ -9,19 +7,11 @@
  * ... and again Southern-Winter 2001 to support export_operations
  */
 
-#include <linux/slab.h>
-#include <linux/fs.h>
-#include <linux/unistd.h>
-#include <linux/string.h>
-#include <linux/stat.h>
-#include <linux/dcache.h>
 #include <linux/exportfs.h>
-#include <linux/mount.h>
 
-#include <linux/sunrpc/clnt.h>
-#include <linux/sunrpc/svc.h>
 #include <linux/sunrpc/svcauth_gss.h>
-#include <linux/nfsd/nfsd.h>
+#include "nfsd.h"
+#include "vfs.h"
 #include "auth.h"
 
 #define NFSDDBG_FACILITY                NFSDDBG_FH
@@ -96,8 +86,10 @@ nfsd_mode_check(struct svc_rqst *rqstp, umode_t mode, int type)
 static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
                                           struct svc_export *exp)
 {
+        int flags = nfsexp_flags(rqstp, exp);
+
         /* Check if the request originated from a secure port. */
-        if (!rqstp->rq_secure && EX_SECURE(exp)) {
+        if (!rqstp->rq_secure && (flags & NFSEXP_INSECURE_PORT)) {
                 RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
                 dprintk(KERN_WARNING
                        "nfsd: request from insecure port %s!\n",
@@ -109,6 +101,36 @@ 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
@@ -232,14 +254,6 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
                 goto out;
         }
 
-        if (exp->ex_flags & NFSEXP_NOSUBTREECHECK) {
-                error = nfsd_setuser_and_check_port(rqstp, exp);
-                if (error) {
-                        dput(dentry);
-                        goto out;
-                }
-        }
-
         if (S_ISDIR(dentry->d_inode->i_mode) &&
                         (dentry->d_flags & DCACHE_DISCONNECTED)) {
                 printk("nfsd: find_fh_dentry returned a DISCONNECTED directory: %s/%s\n",
@@ -294,28 +308,32 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
                 error = nfsd_set_fh_dentry(rqstp, fhp);
                 if (error)
                         goto out;
-                dentry = fhp->fh_dentry;
-                exp = fhp->fh_export;
-        } else {
-                /*
-                 * just rechecking permissions
-                 * (e.g. nfsproc_create calls fh_verify, then nfsd_create
-                 * does as well)
-                 */
-                dprintk("nfsd: fh_verify - just checking\n");
-                dentry = fhp->fh_dentry;
-                exp = fhp->fh_export;
-                /*
-                 * Set user creds for this exportpoint; necessary even
-                 * in the "just checking" case because this may be a
-                 * filehandle that was created by fh_compose, and that
-                 * is about to be used in another nfsv4 compound
-                 * operation.
-                 */
-                error = nfsd_setuser_and_check_port(rqstp, exp);
-                if (error)
-                        goto out;
         }
+        dentry = fhp->fh_dentry;
+        exp = fhp->fh_export;
+        /*
+         * We still have to do all these permission checks, even when
+         * fh_dentry is already set:
+         *      - fh_verify may be called multiple times with different
+         *        "access" arguments (e.g. nfsd_proc_create calls
+         *        fh_verify(...,NFSD_MAY_EXEC) first, then later (in
+         *        nfsd_create) calls fh_verify(...,NFSD_MAY_CREATE).
+         *      - in the NFSv4 case, the filehandle may have been filled
+         *        in by fh_compose, and given a dentry, but further
+         *        compound operations performed with that filehandle
+         *        still need permissions checks.  In the worst case, a
+         *        mountpoint crossing may have changed the export
+         *        options, and we may now need to use a different uid
+         *        (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;
 
         error = nfsd_mode_check(rqstp, dentry->d_inode->i_mode, type);
         if (error)