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[01/15] configfs: fix registered group removal

Message ID 1531696591-8558-2-git-send-email-mchristi@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Mike Christie July 15, 2018, 11:16 p.m. UTC
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>
 fs/configfs/dir.c | 10 ++++++++++
 1 file changed, 10 insertions(+)


Christoph Hellwig July 17, 2018, 1:17 p.m. UTC | #1
Thanks, applied to the configfs tree.

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diff mbox


diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 577cff2..45cdbb5 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -1777,6 +1777,15 @@  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);
 	configfs_detach_prep(dentry, NULL);
@@ -1791,6 +1800,7 @@  void configfs_unregister_group(struct config_group *group)