Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs fixes from Al Viro:
 "The sget() one is a long-standing bug and will need to go into -stable
  (in fact, it had been originally caught in RHEL6), the other two are
  3.11-only"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: constify dentry parameter in d_count()
  livelock avoidance in sget()
  allow O_TMPFILE to work with O_WRONLY

2 files changed, 12 insertions, 15 deletions

diff --git a/fs/open.c b/fs/open.c
index 9156cb050d08..d53e29895082 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -844,6 +844,8 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
                         return -EINVAL;
                 acc_mode = MAY_OPEN | ACC_MODE(flags);
+                if (!(acc_mode & MAY_WRITE))
+                        return -EINVAL;
         } else if (flags & O_PATH) {
                 /*
                  * If we have O_PATH in the open flag. Then we
diff --git a/fs/super.c b/fs/super.c
index 7465d4364208..68307c029228 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -336,19 +336,19 @@ EXPORT_SYMBOL(deactivate_super);
  *      and want to turn it into a full-blown active reference.  grab_super()
  *      is called with sb_lock held and drops it.  Returns 1 in case of
  *      success, 0 if we had failed (superblock contents was already dead or
- *      dying when grab_super() had been called).
+ *      dying when grab_super() had been called).  Note that this is only
+ *      called for superblocks not in rundown mode (== ones still on ->fs_supers
+ *      of their type), so increment of ->s_count is OK here.
  */
 static int grab_super(struct super_block *s) __releases(sb_lock)
 {
-        if (atomic_inc_not_zero(&s->s_active)) {
-                spin_unlock(&sb_lock);
-                return 1;
-        }
-        /* it's going away */
         s->s_count++;
         spin_unlock(&sb_lock);
-        /* wait for it to die */
         down_write(&s->s_umount);
+        if ((s->s_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) {
+                put_super(s);
+                return 1;
+        }
         up_write(&s->s_umount);
         put_super(s);
         return 0;
@@ -463,11 +463,6 @@ retry:
                                 destroy_super(s);
                                 s = NULL;
                         }
-                        down_write(&old->s_umount);
-                        if (unlikely(!(old->s_flags & MS_BORN))) {
-                                deactivate_locked_super(old);
-                                goto retry;
-                        }
                         return old;
                 }
         }
@@ -660,10 +655,10 @@ restart:
                 if (hlist_unhashed(&sb->s_instances))
                         continue;
                 if (sb->s_bdev == bdev) {
-                        if (grab_super(sb)) /* drops sb_lock */
-                                return sb;
-                        else
+                        if (!grab_super(sb))
                                 goto restart;
+                        up_write(&sb->s_umount);
+                        return sb;
                 }
         }
         spin_unlock(&sb_lock);