vfs: fix deadlock in file_remove_privs() on overlayfs

file_remove_privs() is called with inode lock on file_inode(), which
proceeds to calling notify_change() on file->f_path.dentry.  Which triggers
the WARN_ON_ONCE(!inode_is_locked(inode)) in addition to deadlocking later
when ovl_setattr tries to lock the underlying inode again.

Fix this mess by not mixing the layers, but doing everything on underlying
dentry/inode.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 07a2daab49c5 ("ovl: Copy up underlying inode's ->i_mode to overlay inode")
Cc: <stable@vger.kernel.org>

diff --git a/fs/inode.c b/fs/inode.c
index 4ccbc21..68db390 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1740,8 +1740,8 @@ static int __remove_privs(struct dentry *dentry, int kill)
  */
 int file_remove_privs(struct file *file)
 {
-       struct dentry *dentry = file->f_path.dentry;
-       struct inode *inode = d_inode(dentry);
+       struct dentry *dentry = file_dentry(file);
+       struct inode *inode = file_inode(file);
        int kill;
        int error = 0;
 
@@ -1749,7 +1749,7 @@ int file_remove_privs(struct file *file)
        if (IS_NOSEC(inode))
                return 0;
 
-       kill = file_needs_remove_privs(file);
+       kill = dentry_needs_remove_privs(dentry);
        if (kill < 0)
                return kill;
        if (kill)