From: ChenXiaoSong chenxiaosong2@huawei.com

hulk inclusion category: bugfix bugzilla: 186233, https://gitee.com/src-openeuler/kernel/issues/I4TLA2?from=project-issue CVE: NA

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When configfs_register_subsystem() or configfs_unregister_subsystem() is executing link_group() or unlink_group(), it is possible that two processes add or delete list concurrently. Some unfortunate interleavings of them can cause kernel panic.

One of cases is: A --> B --> C --> D A <-- B <-- C <-- D

delete list_head *B | delete list_head *C --------------------------------|----------------------------------- configfs_unregister_subsystem | configfs_unregister_subsystem unlink_group | unlink_group unlink_obj | unlink_obj list_del_init | list_del_init __list_del_entry | __list_del_entry __list_del | __list_del // next == C | next->prev = prev | | next->prev = prev prev->next = next | | // prev == B | prev->next = next

Fix this by adding mutex when calling link_group() or unlink_group(), but parent configfs_subsystem is NULL when config_item is root. So I create a mutex configfs_subsystem_mutex.

Fixes: 7063fbf22611 ("[PATCH] configfs: User-driven configuration filesystem") Signed-off-by: ChenXiaoSong chenxiaosong2@huawei.com Signed-off-by: Laibin Qiu qiulaibin@huawei.com Reviewed-by: yangerkun yangerkun@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/configfs/dir.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 2cc6b1c49d348..9b43611e1bb35 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -50,6 +50,14 @@ DECLARE_RWSEM(configfs_rename_sem); */ DEFINE_SPINLOCK(configfs_dirent_lock);

+/* + * All of link_obj/unlink_obj/link_group/unlink_group require that + * subsys->su_mutex is held. + * But parent configfs_subsystem is NULL when config_item is root. + * Use this mutex when config_item is root. + */ +static DEFINE_MUTEX(configfs_subsystem_mutex); + static void configfs_d_iput(struct dentry * dentry, struct inode * inode) { @@ -1936,7 +1944,9 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys) group->cg_item.ci_name = group->cg_item.ci_namebuf;

sd = root->d_fsdata; + mutex_lock(&configfs_subsystem_mutex); link_group(to_config_group(sd->s_element), group); + mutex_unlock(&configfs_subsystem_mutex);

inode_lock_nested(d_inode(root), I_MUTEX_PARENT);

@@ -1961,7 +1971,9 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys) inode_unlock(d_inode(root));

if (err) { + mutex_lock(&configfs_subsystem_mutex); unlink_group(group); + mutex_unlock(&configfs_subsystem_mutex); configfs_release_fs(); } put_fragment(frag); @@ -2007,7 +2019,9 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)

dput(dentry);

+ mutex_lock(&configfs_subsystem_mutex); unlink_group(group); + mutex_unlock(&configfs_subsystem_mutex); configfs_release_fs(); }