Messages in this thread Patch in this message | | | From | Masamitsu Yamazaki <> | Subject | [PATCH] ipmi: Clear smi_info->thread to prevent use-after-free during module unload | Date | Mon, 15 Jan 2018 07:58:12 +0000 |
| |
Subject:[PATCH] ipmi: Clear smi_info->thread to prevent use-after-free during module unload To: Corey Minyard <minyard@acm.org> To: openipmi-developer@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org Cc: j-nomura@ce.jp.nec.com Cc: k-ueda@ct.jp.nec.com Cc: m-yamazaki@ah.jp.nec.com
During code inspection, I found an use-after-free possibility during unloading ipmi_si in the polling mode.
If start_new_msg() is called after kthread_stop(), the function will try to wake up non-existing kthread using the dangling pointer.
Possible scenario is when a new internal message is generated after ipmi_unregister_smi()[*1] and remains after stop_timer_and_thread() in clenaup_one_si() [*2]. Use-after-free could occur as follows depending on BMC replies.
cleanup_one_si => ipmi_unregister_smi [*1] => stop_timer_and_thread => kthread_stop(smi_info->thread) [*2] => poll => smi_event_handler => start_new_msg => if (smi_info->thread) wake_up_process(smi_info->thread) <== use-after-free!!
Although currently it seems no such message is generated in the polling mode, some changes might introduce that in thefuture. For example in the interrupt mode, disable_si_irq() does that at [*2].
So let's prevent such a critical issue possibility now.
Signed-off-by: Yamazaki Masamitsu <m-yamazaki@ah.jp.nec.com>
diff -Nurp a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c --- a/drivers/char/ipmi/ipmi_si_intf.c 2018-01-09 13:40:14.624785104 +0900 +++ b/drivers/char/ipmi/ipmi_si_intf.c 2018-01-09 13:44:39.174780570 +0900 @@ -1938,8 +1938,10 @@ static void check_for_broken_irqs(struct static inline void stop_timer_and_thread(struct smi_info *smi_info) { - if (smi_info->thread != NULL) + if (smi_info->thread != NULL) { kthread_stop(smi_info->thread); + smi_info->thread = NULL; + } smi_info->timer_can_start = false; if (smi_info->timer_running)
| |