[PATCH] autofs4: avoid panic on bind mount of autofs owned directory

While this is not a solution to bind and move mounts on autofs owned
directories it is necessary to fix the trady error handling.

At least it avoids the kernel panic I observed checking out bug #4589.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 3765c047f157..e137acf0543d 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -205,7 +205,11 @@ static int autofs4_dir_open(struct inode *inode, struct file *file)
                 struct vfsmount *fp_mnt = mntget(mnt);
                 struct dentry *fp_dentry = dget(dentry);
 
-                while (follow_down(&fp_mnt, &fp_dentry) && d_mountpoint(fp_dentry));
+                if (!autofs4_follow_mount(&fp_mnt, &fp_dentry)) {
+                        dput(fp_dentry);
+                        mntput(fp_mnt);
+                        return -ENOENT;
+                }
 
                 fp = dentry_open(fp_dentry, fp_mnt, file->f_flags);
                 status = PTR_ERR(fp);