The pstore backend lock wasn't being used during pstore_unregister(). Add sanity check and locking.
Signed-off-by: Kees Cook <[email protected]> --- fs/pstore/platform.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c index d0ce22237589..03bc847a6951 100644 --- a/fs/pstore/platform.c +++ b/fs/pstore/platform.c @@ -69,8 +69,9 @@ static void pstore_dowork(struct work_struct *); static DECLARE_WORK(pstore_work, pstore_dowork); /* - * psinfo_lock just protects "psinfo" during - * calls to pstore_register() + * psinfo_lock protects "psinfo" during calls to + * pstore_register(), pstore_unregister(), and + * the filesystem mount/unmount routines. */ static DEFINE_MUTEX(psinfo_lock); struct pstore_info *psinfo; @@ -626,6 +627,18 @@ EXPORT_SYMBOL_GPL(pstore_register); void pstore_unregister(struct pstore_info *psi) { + /* It's okay to unregister nothing. */ + if (!psi) + return; + + mutex_lock(&psinfo_lock); + + /* Only one backend can be registered at a time. */ + if (WARN_ON(psi != psinfo)) { + mutex_unlock(&psinfo_lock); + return; + } + /* Stop timer and make sure all work has finished. */ pstore_update_ms = -1; del_timer_sync(&pstore_timer); @@ -644,6 +657,7 @@ void pstore_unregister(struct pstore_info *psi) psinfo = NULL; backend = NULL; + mutex_unlock(&psinfo_lock); } EXPORT_SYMBOL_GPL(pstore_unregister); -- 2.20.1
