autofs4: Fix wait validation

It is possible for the check in wait.c:validate_request() to return
an incorrect result if the dentry that was mounted upon has changed
during the callback.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 16 insertions, 1 deletions

diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index c5f8459c905e..56010056b2e6 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -309,6 +309,9 @@ static int validate_request(struct autofs_wait_queue **wait,
          * completed while we waited on the mutex ...
          */
         if (notify == NFY_MOUNT) {
+                struct dentry *new = NULL;
+                int valid = 1;
+
                 /*
                  * If the dentry was successfully mounted while we slept
                  * on the wait queue mutex we can return success. If it
@@ -316,8 +319,20 @@ static int validate_request(struct autofs_wait_queue **wait,
                  * a multi-mount with no mount at it's base) we can
                  * continue on and create a new request.
                  */
+                if (!IS_ROOT(dentry)) {
+                        if (dentry->d_inode && d_unhashed(dentry)) {
+                                struct dentry *parent = dentry->d_parent;
+                                new = d_lookup(parent, &dentry->d_name);
+                                if (new)
+                                        dentry = new;
+                        }
+                }
                 if (have_submounts(dentry))
-                        return 0;
+                        valid = 0;
+
+                if (new)
+                        dput(new);
+                return valid;
         }
 
         return 1;