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>

diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index c5f8459c905e6453206c585df1eedb65a89dfef1..56010056b2e6d9001280597b73146ccb839d1b87 100644 (file)
--- 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;