4.18-stable review patch. If anyone has any objections, please let me know.
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From: Mike Christie mchristi@redhat.com
[ 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 mchristi@redhat.com Cc: Christoph Hellwig hch@lst.de Cc: Joel Becker jlbec@evilplan.org Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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); }