From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mike Christie , Christoph Hellwig , Joel Becker , Sasha Levin Subject: [PATCH 4.14 118/173] configfs: fix registered group removal Date: Mon, 24 Sep 2018 13:52:32 +0200 Message-Id: <20180924113124.695436699@linuxfoundation.org> In-Reply-To: <20180924113114.334025954@linuxfoundation.org> References: <20180924113114.334025954@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mike Christie [ Upstream commit cc57c07343bd071cdf1915a91a24ab7d40c9b590 ] 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 Cc: Christoph Hellwig Cc: Joel Becker Signed-off-by: Christoph Hellwig Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/configfs/dir.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -1777,6 +1777,16 @@ void configfs_unregister_group(struct co 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 co dput(dentry); mutex_lock(&subsys->su_mutex); +unlink_group: unlink_group(group); mutex_unlock(&subsys->su_mutex); }