Commit 75f0b68b authored by Nicolai Stange's avatar Nicolai Stange Committed by Greg Kroah-Hartman
Browse files

debugfs: open_proxy_open(): avoid double fops release

Debugfs' open_proxy_open(), the ->open() installed at all inodes created
through debugfs_create_file_unsafe(),
- grabs a reference to the original file_operations instance passed to
  debugfs_create_file_unsafe() via fops_get(),
- installs it at the file's ->f_op by means of replace_fops()
- and calls fops_put() on it.

Since the semantics of replace_fops() are such that the reference's
ownership is transferred, the subsequent fops_put() will result in a double
release when the file is eventually closed.

Currently, this is not an issue since fops_put() basically does a
module_put() on the file_operations' ->owner only and there don't exist any
modules calling debugfs_create_file_unsafe() yet. This is expected to
change in the future though, c.f. commit c6468808 ("debugfs: add
support for self-protecting attribute file fops").

Remove the call to fops_put() from open_proxy_open().

Fixes: 9fd4dcec

 ("debugfs: prevent access to possibly dead
                      file_operations at file open")
Signed-off-by: default avatarNicolai Stange <nicstange@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b10e3e90
......@@ -127,7 +127,6 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
r = real_fops->open(inode, filp);
out:
fops_put(real_fops);
debugfs_use_file_finish(srcu_idx);
return r;
}
......
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