Commit cc57c073 authored Jul 15, 2018 by Mike Christie Committed by Christoph Hellwig Jul 17, 2018

configfs: fix registered group removal



This patch fixes a bug where configfs_register_group had added
a group in a tree, and userspace has done a rmdir on a dir somewhere
above that group and we hit a kernel crash. The problem is configfs_rmdir
will detach everything under it and unlink groups on the default_groups
list. It will not unlink groups added with configfs_register_group so when
configfs_unregister_group is called to drop its references to the group/items
we crash when we try to access the freed dentrys.

The patch just adds a check for if a rmdir has been done above
us and if so just does the unlink part of unregistration.

Sorry if you are getting this multiple times. I thouhgt I sent
this to some of you and lkml, but I do not see it.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

parent 1823342a

fs/configfs/dir.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -1777,6 +1777,16 @@ void configfs_unregister_group(struct config_group *group)
		struct dentry *dentry = group->cg_item.ci_dentry;
		struct dentry *parent = group->cg_item.ci_parent->ci_dentry;

		mutex_lock(&subsys->su_mutex);
		if (!group->cg_item.ci_parent->ci_group) {
		/*
		* The parent has already been unlinked and detached
		* due to a rmdir.
		*/
		goto unlink_group;
		}
		mutex_unlock(&subsys->su_mutex);

		inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
		spin_lock(&configfs_dirent_lock);
		configfs_detach_prep(dentry, NULL);
		@@ -1791,6 +1801,7 @@ void configfs_unregister_group(struct config_group *group)
		dput(dentry);

		mutex_lock(&subsys->su_mutex);
		unlink_group:
		unlink_group(group);
		mutex_unlock(&subsys->su_mutex);
		}

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